There's a lot wrong here but I'll try and correct as much as I can

Item 1

https://backpack.tf/item/11068385574

Sale 1

https://backpack.tf/profiles/76561198109141608#!/compare/1647043200/1647129600

https://backpack.tf/profiles/76561198850274253#!/compare/1647043200/1647129600

Bulk

Sale 2

https://backpack.tf/profiles/76561198850274253#!/compare/1648944000/1649030400

https://backpack.tf/profiles/76561198055820194#!/compare/1647820800/1649721600

Untrace

Item 2

https://backpack.tf/item/11007534080

Sale 3

https://backpack.tf/profiles/76561198080114979#!/compare/1646956800/1647043200

https://backpack.tf/profiles/76561198081129776#!/compare/1646611200/1647043200

7 keys 34 ref match

Item 3

https://backpack.tf/item/10999077595

Sale 4

https://backpack.tf/profiles/76561198361999761#!/compare/1643932800/1644019200

https://backpack.tf/profiles/76561199106931116#!/compare/1643932800/1644019200

1 key matches

Sale 5

https://backpack.tf/profiles/76561199106931116#!/compare/1646611200/1646697600

https://backpack.tf/profiles/76561198402082466#!/compare/1646697600/1646784000

18 keys

Item 4

https://backpack.tf/item/4844460717

Sale 6

https://marketplace.tf/items/tf2/30616;5;u3084

Mar 22nd - $36.99 / $1.74 = 21.26 keys

Sales

7.5, 18, 21

And perhaps ~12

Realistically sales are all over the place, I'd rather leave this outdated.

It was already a little odd to range with the 12 key unsold and your 18 key purchase

Wait for a mod