Your... Fez is Familiar. Eheheheheh

https://backpack.tf/item/3791339429

Sale 1) Sold for 30 Keys + 1 Key of Refined

https://backpack.tf/profiles/76561198081270783#!/compare/1540857600/1540944000

Low outlier.

Sale 2) Sold for a Circling Peace Sign Samur-Eye (17.75 Keys) + Steaming Warhood (13 Keys) + Aces High Pirate Bandana (12 Keys)

https://backpack.tf/profiles/76561198204824055#!/compare/1540944000/1541030400 - Seller's Backpack

https://backpack.tf/profiles/76561198853349499#!/compare/1540944000/1541030400 - Buyer's Backpack

17.75 + 13 + 12 = 42.75, which rounds to 43 Keys

Samur-Eye Mini

https://backpack.tf/suggestion/5c287bc6cf6c75679872ec3e - Marketplace sale at 19 Keys and the sale for the Mirror at 16.5 Keys

Warhood Mini

https://backpack.tf/profiles/76561198204824055#!/compare/1540944000/1541030400 - Sold for 13 Keys + 1 Refined

Bandana Mini

https://backpack.tf/suggestion/5c2870bacf6c755f8c4e7313 - 12 Keys

https://marketplace.tf/items/223;5;u89 - Sold for $74 when Keys were ~$1.79 each

https://marketplace.tf/items/5021;6/Mann%20Co.%20Supply%20Crate%20Key

74 / 1.79 = 41.34, which rounds to 41 Keys

https://imgur.com/a/C58tJOG - 5 Day Seller at 38 Keys. 24 Day Seller at 30 Keys.

https://backpack.tf/item/3791339429

https://backpack.tf/item/6586483015