Sale 1:

Sold for 4 keys + ~4 keys in items

Seller: https://backpack.tf/profiles/76561198126868108#!/compare/1523491200/1523577600

Buyer: https://backpack.tf/profiles/76561198820949081#!/compare/1523577600/1523664000

X = 8

Sale 2:

Sold for 7 keys

Seller: https://backpack.tf/profiles/76561198289285442#!/compare/1523491200/1523577600

Buyer: https://backpack.tf/profiles/76561198289285442#!/compare/1523491200/1523577600

X = 7

Sale 3:

Sold with 2 keys + small amount of ref for Slumber Wing Mann

No outpost

Seller: https://backpack.tf/profiles/76561198375162968#!/compare/1523491200/1523577600

Buyer: https://backpack.tf/profiles/76561198126868108#!/compare/1523491200/1523577600

Don’t wanna use this without a B/O

Sellers:

15 keys:

https://i.imgur.com/5e1iSlT.png

https://backpack.tf/item/5405298854

17 keys:

https://i.imgur.com/Au5NWaT.png

https://backpack.tf/item/5354317756

22 keys:

https://i.imgur.com/1PigVPc.png

https://backpack.tf/item/5366498597

Sales at:

7

8

Going with 7-8.

Seller at 15 keys sold to a bot for 5 keys + 8 ref:

https://backpack.tf/profiles/76561198820949081#!/compare/1523577600/1523664000

Being re-sold for ~8.5 keys:

https://i.imgur.com/7mobSWW.png

https://backpack.tf/item/5405298854

Buyer has (re)appeared at 8 keys:

https://i.imgur.com/h8W6grP.png

Gonna wait a bit and see if it remains, because the next highest buyer is ~5.4 keys.