Ghostbusters

https://backpack.tf/item/4682778662

Sale 1) ?

https://backpack.tf/profiles/76561198080179568#!/compare/1558656000/1558742400

https://backpack.tf/item/269616902

Sale 2) Bulk sale for a Morning Glory Wraith Wrap

https://backpack.tf/profiles/76561198452545626#!/compare/1555977600/1556064000

Sale 3) Sold + 1 Key for a Cloud 9 Warhood (18.5 Keys) + Kill-a-Watt Hot Dogger (16.5 Keys)

https://backpack.tf/profiles/76561198132527164#!/compare/1556323200/1556409600

https://backpack.tf/profiles/76561198261268231#!/compare/1556323200/1556409600

18.5 + 16.5 - 1 = 34 Keys

Dogger Mini

https://backpack.tf/profiles/76561198318716514#!/compare/1557878400/1557964800 - Bought for 15 Keys + 10 Refined

https://backpack.tf/profiles/76561198318716514#!/compare/1557878400/1557964800 - Sold for an Atomic Universal Translator (15 Keys)

https://backpack.tf/profiles/76561198157558571#!/compare/1554508800/1554595200 - Sold for 15 Keys

https://backpack.tf/profiles/76561198384785399#!/compare/1561161600/1561248000 - Sold for 14 Keys + ~1 Key of Items

https://marketplace.tf/items/tf2/614;5;u56 - Sold for $30 when Keys were ~$1.78 each, $39.99 (high), $20 (low), and $33.33 when Keys were ~$1.83 each

https://marketplace.tf/items/tf2/5021;6

30 / 1.78 = 16.85, which rounds to 17 Keys

33.33 / 1.83 = 18.21, which rounds to 18 Keys

Sale 4) ?

https://backpack.tf/profiles/76561198261268231#!/compare/1560297600/1561334400

https://imgur.com/a/t9cg4vd - Seller with 2 at 30.15 and 30.48 Keys

https://backpack.tf/item/4682778662

https://backpack.tf/item/269616902