Sale 1:

https://backpack.tf/profiles/76561198200568586#!/compare/1561593600/1561852800

https://backpack.tf/profiles/76561198964919488#!/compare/1561507200/1562112000

untrace

Sale 2:

https://backpack.tf/profiles/76561198050518375#!/compare/1563494400/1563580800

https://backpack.tf/profiles/76561198002757046#!/compare/1563494400/1563580800

Sold for 8 keys

Sale 3:

https://backpack.tf/profiles/76561198002757046#!/compare/1565136000/1565222400

https://backpack.tf/profiles/76561198867972665#!/compare/1565136000/1565222400

Sold for ~9 keys

Sale 4:

https://backpack.tf/profiles/76561198867972665#!/compare/1565222400/1565308800

https://backpack.tf/profiles/76561198962871067#!/compare/1565222400/1565308800

Untrace

Sale 5:

https://backpack.tf/profiles/76561198079200282#!/compare/1561680000/1561766400'

https://backpack.tf/profiles/76561198006544512#!/compare/1561593600/1561680000

Sold for ~8 keys

Sale 6:

https://backpack.tf/profiles/76561198337734785#!/compare/1559779200/1559865600

https://backpack.tf/profiles/76561198060159980#!/compare/1559865600/1559952000

Sold for 9 keys

Sale 7:

https://backpack.tf/profiles/76561198060159980#!/compare/1559952000/1560124800

https://backpack.tf/profiles/76561198171909991#!/compare/1559865600/1560038400

Can trace ref..

Sale 8:

https://backpack.tf/profiles/76561198171909991#!/compare/1560384000/1560470400

https://backpack.tf/profiles/76561198068351675#!/compare/1560297600/1560470400

Bulky

Sale 9:

https://backpack.tf/profiles/76561198068351675#!/compare/1560297600/1560470400

https://backpack.tf/profiles/76561198154083889#!/compare/1560384000/1560470400

Sold for TW Birdcage

use there

Sale 10:

https://backpack.tf/profiles/76561198154083889#!/compare/1560470400/1560556800

https://backpack.tf/profiles/76561198140083209#!/compare/1560470400/1560556800

Sold for 9 keys (8 used to buy Sky High)

Sale 11:

https://backpack.tf/profiles/76561198140083209#!/compare/1560470400/1560556800

https://backpack.tf/profiles/76561198137412734#!/compare/1540425600/1560556800

Untrace

Sale 12:

https://backpack.tf/profiles/76561198137412734#!/compare/1540425600/1560556800

https://backpack.tf/profiles/76561198186922501#!/compare/1560384000/1560556800

Sold for Spell

Sale 13:

https://backpack.tf/profiles/76561198186922501#!/compare/1561680000/1562112000

https://backpack.tf/profiles/76561198006544512#!/compare/1561593600/1561680000

QS

Sale 14:

https://backpack.tf/profiles/76561198302622799#!/compare/1563667200/1563840000

https://backpack.tf/profiles/76561198398476585#!/compare/1563753600/1563840000

Sold for 8 keys

Sale 15:

https://backpack.tf/profiles/76561198029074524#!/compare/1564185600/1564358400

https://backpack.tf/profiles/76561198101300189#!/compare/1564185600/1564272000

https://backpack.tf/profiles/76561198323565601#!/compare/1564185600/1564272000

Untrace

Sale 16:

https://marketplace.tf/items/tf2/30978;5;u6

https://backpack.tf/item/7805224298

$15.57 / $1.80 = 8.65 keys

total sales @:

8, 8, 8, 8.65, 9, 9, 9 keys

Taking 8 - 9 keys.