Somehow slightly Inspired by @DanaDigsYou and her Girl Scout Cookie list...
  1. Ron sells all his cookies to Fred and George and thinks it's because they really, actually like him, but actually they just resell them and turn a profit.
  2. Hermione buys up a fair amount of her own cookies after exchanging her muggle money at the ATM outside the Great Hall, and donates them to local food shelters.
  3. Draco sells exclusively Trefoils because they're white.
  4. Dean Thomas upcharges his cookies to Hufflepuffs.
  5. Hannah Abbott gets to Hagrid first.
  6. Crabbe and Goyle eat all their boxes of cookies without realizing they have to pay for them if they don't sell them, so then they just steal the money from Justin Finch-Fletchy and leave him hanging by his wedgie from a candelabra.
  7. Seamus smuggles cookies from evening feasts to restock used boxes to keep selling off-season.
  8. Neville forgets to sell any cookies.
  9. Harry Potter just uses his inheritance to buy all his cookies so he doesn't have to sell any and can still beat everyone else.