Deadly Bomb

https://backpack.tf/item/3973895794

Sale 1) Sold for 23 Keys

https://backpack.tf/profiles/76561198118355049#!/compare/1524009600/1524096000

Low outlier.

Sale 2) Sold for a Purple Energy Armored Authority

https://backpack.tf/profiles/76561198054758757#!/compare/1526169600/1526256000

There's no Mini for the Armored.

Sale 3) Sold for a Memory Leak Wraith Wrap (37 Keys) + 4 Keys

https://backpack.tf/profiles/76561198355397641#!/compare/1530748800/1531180800

37 + 4 = 41 Keys

Wraith Mini

https://backpack.tf/suggestion/5b48e0d5cf6c7553bd236539 - 37 Keys

Sale 4) Sold for a Duped Scorching Flames German Gonzila (39.5 Keys)

https://backpack.tf/profiles/76561198086793593#!/compare/1531267200/1531353600

Rounds to 40 Keys

German Mini

https://backpack.tf/profiles/76561198086793593#!/compare/1531353600/1531440000 - Sold + 2 Keys for an Orbiting Fire Galvanized Gibus

https://backpack.tf/profiles/76561198090339904#!/compare/1531353600/1531440000 - Sold + 2 Keys for a Starstorm Insomnia Gibus (42.5 Keys)

https://backpack.tf/profiles/76561197997268820#!/compare/1529107200/1529193600 - Sold for a Neutron Star Kiss King + 11 Keys

https://backpack.tf/profiles/76561198313538268#!/compare/1526947200/1527033600 - Sold for 38 Keys

Taking 38 - 41

https://marketplace.tf/items/30547;5;u90 - Sold for $80 when Keys were ~$1.97 each and $70 when they were ~$1.96 each

80 / 1.97 = 40.6, which rounds to 41 Keys

70 / 1.96 = 35.7, which rounds to 36 Keys