Sale 1:

Sold for 7 keys

Seller: https://backpack.tf/profiles/76561198386441509#!/compare/1522454400/1522540800

Buyer: https://backpack.tf/profiles/76561198050974286#!/compare/1495324800/1522713600

Bot.tf confirms: https://i.imgur.com/XzkFEsv.png

This sale’s untraceable without bot.tf, but given the other sale had ref involved, we can safely say that this one was the one that sold for 7 keys

X = 7

Sale 2:

Sold for 6 keys + 15 ref

Seller: https://backpack.tf/profiles/76561198442764620#!/compare/1521849600/1521936000

Buyer: https://backpack.tf/profiles/76561198161977280#!/compare/1521849600/1521936000 (couldn’t get a better link on this end)

Bot.tf confirms: https://i.imgur.com/XzkFEsv.png

X = 6.5

Sale 3:

Bulk for Subatomic Universal Translator

Seller: https://backpack.tf/profiles/76561198336622852#!/compare/1523318400/1523404800

Buyer: https://backpack.tf/profiles/76561198360414117#!/compare/1523232000/1523404800

Sale 4:

Bulk for Blizzardy Storm Human Cannonball

Seller: https://backpack.tf/profiles/76561198360414117#!/compare/1523232000/1523404800

Buyer: https://backpack.tf/profiles/76561198021055079#!/compare/1523318400/1523404800

Sellers:

7 keys:

https://i.imgur.com/UIknF3h.png

https://backpack.tf/item/6739346120

9 keys:

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

https://backpack.tf/item/4502253010

~22.4 keys:

https://i.imgur.com/i0Samfi.png

https://backpack.tf/item/4423579067

50 keys:

http://www.tf2outpost.com/trade/28672989

Sales at:

6.5

7

Going with 6.5-7.