The necessity of the Four-House Consumer Alliance instantly rewired the dynamics of the Muggle Studies class. The pure-blood wizards, who had arrived with their 25p allowances, suddenly realized their financial and informational dependence on their Muggle-born and Half-blood peers.
Their survival in this strange retail ecosystem hinged entirely on knowing the difference between a good deal and overpriced packaged air.
Marcus Flint, Oliver Wood, and Charlie Weasley quickly secured their last two essential components: Elara Finch, a bright-eyed Third-Year Hufflepuff who, as a Muggle-born, possessed invaluable market knowledge; and Padma Patil, a Seventh-Year Ravenclaw who valued the systematic planning involved.
They had successfully assembled a rare Senior Super-Group of five—three seventh-years, one sixth-year, and one third-year—boasting a cumulative purchasing power of £1.25 (Flint had contributed an extra 25p, ensuring the team was slightly over the minimum capital requirement, a shrewd investment).
Elara Finch, the smallest member of the group, was immediately propelled into the role of lead consultant. She navigated the endless, dazzling aisles with the confidence of a seasoned explorer, lecturing her senior peers on basic economics.
"Right, if we want maximum flavor-per-penny, we need to avoid the single-serving aisle," Elara announced, pointing decisively toward a stack of multi-packs. "Ice cream is out—too hard to split five ways without a spoon charm, and it'll melt before we finish. And soda is expensive."
Charlie and Wood nodded solemnly, hanging on her every word. Marcus Flint, however, looked utterly mesmerized by a display of brightly colored, ridged potato chips.
"What about those? The ones that smell like a roast pig," Marcus asked, pointing to a large bag of BBQ-flavoured crisps. "Surely, a single bag of that salty parchment couldn't cost more than... say, 50p?"
"It's 40p for the family size bag," Elara corrected him precisely. "A single serving is 15p. The BBQ flavor is a good choice, highly ranked in the Muggle Food Quarterly review I read over the summer. But we need a drink, too."
Marcus, fiddling with his pitiful stack of coins, sighed dramatically. "Honestly, the Muggle monetary system is so elegantly simple it's frustrating! The ten-to-one exchange rate—100 pence to the single pound—is logical, immediate, and utterly clear. In the wizarding world, it's a chaotic mess! Twenty-nine Knuts to the Sickle, seventeen Sickles to the Galleon! Every time I try to buy a quill in Diagon Alley, I feel like I need an advanced degree in fractional arithmetic. Why the absurd complexity?"
Padma Patil, the Ravenclaw, nodded in agreement. "The fractional, prime-number-based wizarding exchange rate is a known impediment to economic efficiency. It discourages simple commerce and encourages hoarding. It's entirely too complicated."
"Exactly!" Marcus exclaimed. "And now we're stuck here with one hundred and twenty-five perfectly convertible pence that can barely buy a sandwich! If we only had one Galleon, we could convert it into... well, something worth buying!"
Charlie Weasley's eyes lit up with a spark of Gryffindor audacity. "Wait, we're all older students. We have wealth! If we pool our actual wizarding currency—just one Galleon each—and ask the professor to perform a quick exchange for, say, fifty Muggle pounds, we could buy out the entire snack aisle!"
The idea was infectious. Even Padma, momentarily blinded by the potential for bulk purchasing, smiled.
"I have two Galleons, easily," Wood asserted. "It's brilliant, Charlie! We can solve this liquidity problem instantly!"
Before the five conspirators could collectively turn their hopeful, predatory gaze toward the Knight Bus, Sebastian's voice, amplified and dripping with knowing amusement, cut across the supermarket's canned music.
"ATTENTION, TEAM SENIORITY!" Sebastian boomed, making the speakers vibrate.
"While the Professor is deeply flattered by your desire to exchange your ancestral hoard for Muggle pocket change, and while I commend your quick grasp of the concept of leveraged finance, I regret to inform you: The Foreign Exchange Booth is currently closed. You must work with the financial resources already allocated."
The five conspirators deflated simultaneously. They had been caught.
Marcus Flint, in a desperate attempt to save face and deflect potential professorial wrath, spun around and aimed a blistering, terrified whisper at the others.
"Unbelievable! He denied us! This miserly, penny-pinching, annoyingly handsome..." Marcus's voice cracked as he saw the absolute horror on the faces of his teammates, particularly Charlie Weasley and Oliver Wood, who were slowly backing away from him as if he were covered in highly contagious, dangerous fungus.
Oh, Salazar's beard, I said it out loud! Marcus thought, sweat prickling his forehead. He heard the 'miserly' comment! If he cancels my allowance, I'll be stuck eating boiled cabbages for a week! They're abandoning me!
"Wait! Wait, you fools!" Marcus hissed at his rapidly retreating Gryffindor comrades. He plastered a sickening, entirely false expression of philosophical enlightenment onto his face. "Please, don't misunderstand my passion! I meant that the Professor is genius! I was engaging in rhetorical provocation to test the limits of our assignment!"
He physically grabbed Wood's sleeve before he could escape. "Think about it! If he were generous, we wouldn't need to cooperate! He is willingly sacrificing his reputation for immediate, overwhelming generosity solely for our educational benefit! He wants us to understand the hard-won joy of collaboration over the ease of inherited wealth! He is the greatest, most strategically stingy genius of our time! Don't you all agree?"
Charlie and Wood stared at the performance. Wood looked genuinely nauseated. "Did he just get hit with a Confoundus Charm?"
Charlie, however, merely sighed and stepped forward, placing a bracing, heavy hand on Flint's shoulder. "He's absolutely right, Wood. Don't you see the subtle brilliance?" Charlie's tone was excessively, obviously sarcastic, but he kept his voice level for the professor's benefit.
"Professor Swann is willing to endure the ignominy of being called a 'miser' by a simple-minded student like Flint here, all so we can learn a valuable lesson. We shouldn't let his noble suffering be in vain!"
Charlie shot a look at Marcus that promised a painful reprisal on the Quidditch pitch, then raised his voice slightly. "Thank you for the guidance, Professor! We understand the importance of making sacrifices for the greater good of the group's snack supply!"
Marcus sagged with relief, silently mouthing "Thank you" to Charlie. He knew he was indebted to the Gryffindor Captain—a debt he would have to pay, probably in the form of extra practice sessions or some other Quidditch misery. The shame of being forced to praise a Gryffindor was almost worse than the shame of the 25p.
With the currency crisis settled, the five returned to the arduous task of compromise.
"Right, one hundred and twenty-five pence," Padma stated, reviewing her list of price tags. "We cannot afford the large sharing box of biscuits and two cans of cola. That's 140p."
"We need the cola," Marcus insisted. "It's vital for energy transfer. And it's a status symbol. We can't return to the bus having only purchased a single turnip."
"A turnip is 12p, Flint. That's a 90% profit margin on a 10p investment," Elara countered, already a better financier than most of Gringotts. "But fine. Cola is necessary. Two 35p cans is 70p. That leaves us with 55p."
Charlie interjected, "We need something substantial to share. The BBQ chips. 40p."
"Agreed," Padma said, quickly calculating. "70p plus 40p is 110p. We have 15p remaining. We can purchase three single packets of generic mints for 5p each. That is a perfect, divisible purchase with no waste. Consensus achieved."
The transaction was executed swiftly and efficiently, a rare moment of seamless inter-house cooperation driven by sheer hunger.
As they made their way back to the bus, Sebastian's scrying charms showed him the results of the collective effort. The scene was vastly different from the one he had witnessed just an hour ago.
The bus, which had been sharply divided by House, was now a tapestry of mixed groups. They were sticky-fingered, giggling, and sharing the spoils.
Team Gryffindor-Slytherin-Ravenclaw-Hufflepuff (Senior): Sipping two cans of cola (shared using disposable cups provided on the bus) and passing around the enormous bag of BBQ crisps. Flint, despite his earlier outrage, looked blissful.
Team All-Girls (Hufflepuff/Ravenclaw/Gryffindor): They had pooled their funds and strategically purchased large quantities of inexpensive, high-volume items: grapes, bananas, and a bag of oranges. A remarkably efficient, budget-conscious choice.
Team Quirky (All Houses, Third Year): This group had opted out of the food economy entirely. They had bought two bottles of concentrated bubble solution and were taking turns blowing enormous, rainbow-sheen bubbles inside the stationary Knight Bus—a cheap form of entertainment that generated maximum fun-per-penny.
Perfect, Sebastian thought, suppressing a satisfied grin. The financial constraint was the necessary friction to generate the social heat.
Upon arrival back at the Hogwarts gates, Sebastian retrieved the bag of wands.
"Alright, everyone, focus up!" Sebastian commanded, passing wands back to their respective owners. "It is currently 6:10 PM. You have a well-deserved, slightly messy dinner awaiting you in the Great Hall. But first, two administrative announcements."
The excitement in the air was palpable, but the students quickly silenced themselves, eager to hear what came next.
"First, your homework for the next two weeks is a simple, analytical essay: 'A Comparative Analysis of Retail Efficiency: Diagon Alley vs. the Muggle Supermarket.' I want you to contrast the economics, the logistics, the social utility, and the sensory experience of shopping in both worlds. Be thorough and analytical."
He paused, his gaze sweeping over the older students, particularly the ambitious Fifth Years preparing for their O.W.L.s.
"Secondly, Fifth Years, listen closely. I have determined that the current O.W.L. for Muggle Studies is an utterly irrelevant metric for selecting students for the advanced Sixth- and Seventh-Year course, as the exam is now laughably easy to pass. Therefore, the traditional O.W.L. score will no longer be the primary selection criteria for my advanced classes."
A ripple of shock and interest went through the senior students.
"Instead," Sebastian continued, his voice taking on a serious, focused edge, "admission to the Sixth-Year Innovation Mandate class will be based on the quality, originality, and depth of analysis shown in your upcoming essays and projects. If you wish to join the advanced class and help forge a better magical world, you must take your assignments very, very seriously. The class times for the new, separated sessions will be announced via the common rooms next week."
Sebastian paused for a beat, letting the academic seriousness sink in. Then, he smiled—a wide, theatrical, utterly disarming smile that reached his eyes.
"Finally," Sebastian said, reaching into his deepest, most deceptively stretched velvet bag, "to celebrate the successful completion of today's highly collaborative lesson, and to reward your remarkable spirit of inter-house unity..."
He opened the bag. With a magnificent, non-verbal Duplicating Charm, hundreds of bottles of cola and packets of sugary sweets soared out, filling the air with a cascade of carbonated promises.
The young wizards gasped, staring at the bounty.
"You are each hereby awarded a prize," Sebastian announced, as the items flew toward their designated owners, landing softly in their hands.
"Two full-sized bottles of the finest Muggle-grade soda, and two packets of high-end, highly caloric Muggle sweets. You may consume these yourself, or you may share them with your friends who were unfortunate enough to miss this highly enlightening session. The choice is yours."
The students, who had just spent an hour agonizing over purchasing a shared sip of a single can of cola, were now suddenly holding a vast, personal treasure trove of Muggle luxury.
The earlier financial misery was instantly forgotten, replaced by a surge of ecstatic, grateful loyalty. The memory of the "miserly" professor vanished in the glow of the lavish benefactor.
"Now," Sebastian finished, waving his hand dismissively toward the castle's massive oak doors, "I suggest you all sprint to the Great Hall before the House Elves realize their dessert stock is about to be completely ignored. Dismissed!"
The collective cheer that erupted was deafening. The students, sticky, sugar-hyped, and now richer than they had been an hour ago, stormed the castle doors, the echoes of their shared, collaborative joy ringing across the grounds.