Crocodile Dun-dead.

https://backpack.tf/item/324651971

Sale 1) Sold for a Disco Beat Down Cold Killer (42.5 Keys) + Collector's Darwin's Danger Shield (13 Keys)

https://backpack.tf/profiles/76561198045232326#!/compare/1510272000/1510358400

42.5 + 13 = 55.5, which I'll round down to 55 Keys

Cold Killer Mini

https://backpack.tf/suggestion/5a2c09d2cf6c7538d835ab75 - 42.5 Keys

Sale 2) Sold + 7 Keys for a Cloud 9 Master's Yellow Belt (50.5 Keys)

https://backpack.tf/profiles/76561198180186261#!/compare/1511740800/1511827200 - Buyer's Backpack

50.5 - 7 = 43.5, which rounds to 44 Keys

Sale 3) Sold for 37 Keys

https://backpack.tf/profiles/76561198180186261#!/compare/1511827200/1511913600

Sale 4) Quicksold for 34 Keys

https://backpack.tf/profiles/76561198326093863#!/compare/1511827200/1511913600

http://www.tf2outpost.com/trade/28841809 - 8 Month Unsold at 55 Keys

Counting 37 Keys as low and going with a conservative drop of 44 - 55 Keys.