Sale 1: Untrace.

https://backpack.tf/profiles/76561198197215790#!/compare/1554854400/1555113600

https://backpack.tf/profiles/76561198132741569#!/compare/1554940800/1555027200

Sale 2: Untrace.

https://backpack.tf/profiles/76561198353947264#!/compare/1554768000/1559952000

https://backpack.tf/profiles/76561198080179568#!/compare/1554681600/1554768000

Sale 3: ~20 Keys Pure.

https://backpack.tf/profiles/76561198080179568#!/compare/1559347200/1559433600

https://backpack.tf/profiles/76561198268232003#!/compare/1559347200/1559433600

Sale 4: ~27 Keys. (Calling High)

Sold For Holy Grail Taunt: Conga (21) + 6 Keys = 27 Keys.

https://backpack.tf/profiles/76561198268232003#!/compare/1560729600/1560816000

https://backpack.tf/profiles/76561198140362709#!/compare/1560729600/1560816000

Sale 5: Use There.

Sold With 10 Keys For Molten Mallard Bullet Buzz.

https://backpack.tf/profiles/76561197995221829#!/compare/1555891200/1555977600

https://backpack.tf/profiles/76561198021055079#!/compare/1555891200/1555977600

https://marketplace.tf/items/tf2/30964;5;u62

Sale 6: ~22 Keys. (Calling High, Seller At 20 keys for 2 months)

May 16

$40.00 / $1.82 = 21.98 keys

Sales: 20/22/27

Going with 20 keys flat.

Thanks to scourge for the premium!