Sale 1: ~11 Keys Pure.

https://backpack.tf/profiles/76561198021055079#!/compare/1557532800/1557619200

https://backpack.tf/profiles/76561198093615500#!/compare/1557532800/1557619200

Sale 2: Untrace.

https://backpack.tf/profiles/76561198014417913#!/compare/1551484800/1555977600

https://backpack.tf/profiles/76561198335791307#!/compare/1551830400/1551916800

Sale 3: ~12 Keys Pure.

https://bot.tf/stats/item?def=30959&q=5&ef=Cloud+9&craft=1&aus=0&ks=0

https://backpack.tf/profiles/76561198335791307#!/compare/1556834400/1556920800

Sale 4: Untrace/QS.

https://backpack.tf/profiles/76561198181581553#!/compare/1550793600/1550966400

https://backpack.tf/profiles/76561198308772967#!/compare/1550880000/1550966400

Sale 5: ~12 Keys Pure.

https://backpack.tf/profiles/76561198308772967#!/compare/1551481200/1551567600

Sale 6: Untrace.

https://backpack.tf/profiles/76561198172286358#!/compare/1551571200/1552003200

https://backpack.tf/profiles/76561198120481786#!/compare/1554854400/1558742400

Sale 7: Bulk.

https://backpack.tf/profiles/76561198120481786#!/compare/1554854400/1558742400

https://backpack.tf/profiles/76561198267189538#!/compare/1554768000/1554854400

Sale 8: QS.

https://backpack.tf/profiles/76561198267189538#!/compare/1555113600/1555200000

https://backpack.tf/profiles/76561198308772967#!/compare/1555113600/1555200000

Sale 9: Untrace/Low.

https://backpack.tf/profiles/76561198024867201#!/compare/1552262400/1552348800

https://backpack.tf/profiles/76561198046714413#!/compare/1552262400/1552435200

Marketplace.tf Sales:

https://marketplace.tf/items/30959;5;u58

Sale 10: Low.

Apr 11

$15.10 / $1.77 = 8.53 keys

Sale 11 and 12: ~16 Keys. (Calling high)

Apr 14

$28.99 / $1.77 = 16.38 keys

Usable Sales: 11/12/12

Going with 11-12

Thanks to scourge for the premium!