Sale 1:

Sold for 26 keys + 2 ref

Seller: https://backpack.tf/profiles/76561198060520862#!/compare/1531699200/1531785600

Buyer: https://backpack.tf/profiles/76561198368281005#!/compare/1531699200/1531785600

https://backpack.tf/item/800258834

X = 26

Sale 2:

Sold for 23 keys?

Seller: https://backpack.tf/profiles/76561198337734785#!/compare/1531526400/1531612800

Buyer: https://backpack.tf/profiles/76561198060520862#!/compare/1531526400/1531612800

https://backpack.tf/item/800258834

17 keys match on the buyer’s end, 6 keys appear to have gone to manic: https://backpack.tf/profiles/76561198320810968#!/compare/1531612800/1531699200

Every other key on the buyer’s end went to the same user, so I doubt that I’d be wrong in saying this sold for 23 keys.

X = 23

Sale 3:

Sold to a quickbuyer for 21 keys + some ref

Seller: https://backpack.tf/profiles/76561198084528020#!/compare/1529539200/1529625600

Buyer: https://backpack.tf/profiles/76561198337734785#!/compare/1529539200/1529625600

https://backpack.tf/item/800258834

X = 21

Sellers:

https://i.imgur.com/ToE9quW.png

https://backpack.tf/item/186754604

https://backpack.tf/item/237529168

https://backpack.tf/item/6425595552

Sales at:

21

23

26

21 went to a quickbuyer, excluding.

Going with 23-26.