For Marketplace sales that happened after December 15th, you need to use the average Key price for the week of the sale (day of the sale +/- 3 days).

That'll make the Key price $2.17, which makes the Marketplace sale 50.69 Keys, which will round to 51 Keys.

More Hat to Kill For sales:

https://backpack.tf/profiles/76561198357428287#!/compare/1602547200/1602633600 - The Aces Nunhood was added for the Peak (better for the Peak)

https://backpack.tf/profiles/76561198273331466#!/compare/1603152000/1603238400 - Bulk sale

https://cdn.discordapp.com/attachments/516827733314240517/798759635786924032/unknown.png - The 23 sale was actually 47 Keys

Burning Waxy sales:

https://backpack.tf/profiles/76561198057069564#!/compare/1602288000/1602720000 - 50 Keys

https://backpack.tf/profiles/76561198151373000#!/compare/1602633600/1602720000 - Added 1 Key for a Steaming Bonk Boy (61 Keys)

https://backpack.tf/profiles/76561198850178158#!/compare/1604707200/1604793600 - Strange Original (36 Keys) + MHP Translator + ~9 Keys of Items

https://gladiator.tf/sales?item=Strange+Original - Original sale for 36 Keys

50 - 60 will work as a price for the Waxy

With that, Sale 2 is now 60 Keys. However, since the person who paid 60 resold it in that bulk sale (much less than 60), neither should be used.

47 to 51 Keys will work as a range here.