Sale 1) ?

https://backpack.tf/profiles/76561198119575817#!/compare/1603756800/1603843200

Sale 2) Sold for $49.99 when Keys were ~$1.82 each

https://marketplace.tf/items/tf2/314;5;u10

49.99 / 1.82 = 27.47, which rounds to 27 Keys

Sale 3) Bulk sale

https://backpack.tf/profiles/76561198326511775#!/compare/1605484800/1605571200

Sale 4) Sold for 26 Keys + ~1 Key of Refined

https://backpack.tf/profiles/76561198220098345#!/compare/1606608000/1606694400

26 + 1 = 27 Keys

https://backpack.tf/item/263865601

Sale 5) Sold for 14 Keys?

https://backpack.tf/profiles/76561198100928052#!/compare/1603756800/1603843200

Low outlier

Sale 6) Sold for 28 Keys

https://backpack.tf/profiles/76561198066714060#!/compare/1606262400/1606348800

Excluding because it was resold for 27 and sellers have been lower for a while

Sale 7) Sold for 26 Keys + ~1 Key of Refined

https://backpack.tf/profiles/76561198066714060#!/compare/1606694400/1606867200

26 + 1 = 27 Keys

Sale 8) Bulk sale

https://backpack.tf/profiles/76561197978689903#!/compare/1609804800/1609891200

https://backpack.tf/item/224037936

Sale 9) ?

https://backpack.tf/profiles/76561198138322150#!/compare/1603065600/1603238400

https://imgur.com/a/1TvrmBD - Seller at 26 Keys

https://backpack.tf/item/9096202112