Study

Item 1

https://backpack.tf/item/8735244933

Sale 1

https://backpack.tf/profiles/76561198255331873#!/compare/1593043200/1611187200

https://backpack.tf/profiles/76561199058415641#!/compare/1611014400/1611187200

Untrace

Sale 2

Excluding sales to and from tradeit

Item 2

https://backpack.tf/item/7838149223

Sale 3

https://backpack.tf/profiles/76561198044343775#!/compare/1608940800/1609113600

https://backpack.tf/profiles/76561198850178158#!/compare/1608854400/1608940800

Qsold to qs.store

Sale 4

https://backpack.tf/profiles/76561198850178158#!/compare/1609200000/1609286400

https://backpack.tf/profiles/76561198083488187#!/compare/1606694400/1611619200

Untrace

Item 3

https://backpack.tf/item/7075533837

Sale 5

https://backpack.tf/profiles/76561198334765018#!/compare/1609286400/1609545600

https://backpack.tf/profiles/76561198061182096#!/compare/1609372800/1609632000

Sold for 40 keys

It got painted, that's why ID changed and doesn't match the keys

Marketplace sales

https://marketplace.tf/items/tf2/30623;5;u16

Dec 7th - $89.99 / $1.76 = 51.13 keys

Dec 18th - $89.99 / $2.01 = 44.77 keys

Dec 25th - $99.99 / $2.13 = 46.94 keys

Jan 12th - $99.99 / $2.12 = 47.17 keys

Sales

40, 51, 44, 47, 47

Taking 40 - 51 keys here