Sale 1: ~35 Keys Pure.

https://backpack.tf/profiles/76561198370014787#!/compare/1559433600/1560124800

https://backpack.tf/profiles/76561198278546360#!/compare/1560038400/1560124800

Sale 2: Untrace.

https://backpack.tf/profiles/76561198278546360#!/compare/1561161600/1561248000

https://backpack.tf/profiles/76561198040073503#!/compare/1561161600/1561248000

Sale 3: ~29 Keys Pure. (QS)

https://backpack.tf/profiles/76561198311498888#!/compare/1557014400/1557100800

https://backpack.tf/profiles/76561198330635661#!/compare/1557014400/1557100800

https://stntrading.eu/search?query=Unusual%20Taunt%3A%20The%20Victory%20Lap&isUnusual=1

Sale 4: ~30 Keys Pure.

https://backpack.tf/profiles/76561198330635661#!/compare/1557187200/1557273600

https://backpack.tf/profiles/76561198096009384#!/compare/1557014400/1557273600

Sale 5: Bulk/Use There.

https://backpack.tf/profiles/76561198363231274#!/compare/1558396800/1558569600

https://backpack.tf/profiles/76561198118821301#!/compare/1558483200/1558569600

Sale 6: ~32 Keys Pure.

https://backpack.tf/profiles/76561198092418244#!/compare/1560816000/1560988800

https://backpack.tf/profiles/76561198214243764#!/compare/1560902400/1560988800

https://marketplace.tf/items/tf2/1172;5;u3013

Sale 7: ~36 Keys.

Apr 29

$64.79 / $1.82 = 35.60 keys

Sale 8: ~40 Keys.

May 6

$71.99 / $1.8 = 39.99 keys

Sale 9: ~40 Keys.

May 18

$79.99 / $1.82 = 43.95 keys - B/O was 40 keys ==> https://bot.tf/stats/listings/Y8LWGZX4 - https://backpack.tf/item/6313504255

Sale 10: ~28 Keys. (Bellow Buyer)

Jul 7

$51.56 / $1.83 = 28.17 keys

Sales: 28/29/30/32/35/36/40/40

Going with 30-40 keys

Thanks to scourge for the premium!