Sale 1: Untrace.

https://backpack.tf/profiles/76561198023051867#!/compare/1558742400/1558828800

https://backpack.tf/profiles/76561197998051645#!/compare/1549238400/1561420800

Sale 2: Bellow Buyers.

Sold For Screaming Tiger Taunt: The Trackman's Touchdown (3.25)

https://backpack.tf/profiles/76561198256876413#!/compare/1562112000/1562371200

https://backpack.tf/profiles/76561198881335476#!/compare/1561852800/1562457600

Screaming Tiger Taunt: The Trackman's Touchdown Mini:

https://backpack.tf/suggestion/5d36f9ee6780723fd06c7a30

Sale 3: Untrace. (SCM)

https://backpack.tf/profiles/76561198046321549#!/compare/1557014400/1558915200

https://backpack.tf/profiles/76561197995029705#!/compare/1557792000/1557878400

Sale 4: Untrace/Low.

https://backpack.tf/profiles/76561198305676157#!/compare/1561334400/1561420800

https://backpack.tf/profiles/76561198029074524#!/compare/1561334400/1561420800

Sale 5: ~5.5 Keys Pure.

https://backpack.tf/profiles/76561198021055079#!/compare/1563408000/1563494400

https://backpack.tf/profiles/76561198264858514#!/compare/1563408000/1563580800

https://i.imgur.com/TL0Gxzg.png

https://i.imgur.com/idaVzp0.png - Thanks to jarool.

https://marketplace.tf/items/tf2/30572;5;u3021

Sale 6: ~7 Keys.

May 10

$12.86 / $1.8 = 7.14 keys

Sale 7: ~7 Keys.

May 12

$12.86 / $1.8 = 7.14 keys

Sale 8: ~6.5 Keys.

May 31

$11.69 / $1.81 = 6.46 keys

Sale 9: ~6.5 Keys.

Jun 16

$11.69 / $1.84 = 6.35 keys

Sale 10: ~7 Keys.

Jul 21

$12.36 / $1.81 = 6.83 keys

Sales: 5.5/6.5/6.5/7/7/7

Going with 5.5-7 keys.

Thanks to scourge for the premium!