Kill a Wart

https://backpack.tf/item/7018900651

Sale 1) Sold for 12 Keys + 10 Refined

https://backpack.tf/profiles/76561198032117589#!/compare/1556150400/1556323200

Low outlier.

Sale 2) Quicksold for 13 Keys

https://backpack.tf/profiles/76561198356813033#!/compare/1555977600/1556150400

Sale 3) Quicksold for 13 Keys + 10 Refined

https://backpack.tf/profiles/76561198180923509#!/compare/1556064000/1556150400

Rounds to 13 Keys

https://backpack.tf/item/6799096708

Sale 4) ?

https://backpack.tf/profiles/76561198409819845#!/compare/1552176000/1552262400

https://backpack.tf/profiles/76561198119634686#!/compare/1552089600/1552176000

Sale 5) Sold for 13 Keys

https://backpack.tf/profiles/76561198119634686#!/compare/1554595200/1554681600

https://backpack.tf/item/6798241232

Sale 6) ?

https://backpack.tf/profiles/76561198115246692#!/compare/1555372800/1555459200

https://backpack.tf/item/6239060178

Sale 7) Bulk sale for a Sunbeams Head Full of Hot Air

https://backpack.tf/profiles/76561198150801827#!/compare/1555545600/1555632000

https://backpack.tf/profiles/76561198129564285#!/compare/1555286400/1555545600

Sale 8) Bulk sale for an Australium Rocket Launcher

https://backpack.tf/profiles/76561198129564285#!/compare/1555545600/1555632000

https://backpack.tf/profiles/76561198296497176#!/compare/1555545600/1555632000

https://backpack.tf/item/6765565355

Sale 9) ?

https://backpack.tf/profiles/76561198079967596#!/compare/1556064000/1556150400

https://backpack.tf/profiles/76561198252999692#!/compare/1556064000/1556150400

Sale 10) Quicksold for 12 Keys to a buy order

https://backpack.tf/profiles/76561198252999692#!/compare/1556064000/1556150400

Sale 11) Sold for 13 Keys

https://backpack.tf/profiles/76561198002757046#!/compare/1556582400/1556668800

https://marketplace.tf/items/30866;5;u56 - Sold for $34.99 when Keys were ~$1.77 each

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

34.99 / 1.77 = 19.76, which rounds to 20 Keys