Using last month.

Sale 1:

Sold for $23 on marketplace.tf

https://marketplace.tf/items/1120;5;u3005

http://manicbot.me/keyprice/?at=2018-07-21

Can’t find item’s history.

23/1.95 = ~11.79 keys

X = 12

Sale 2:

Sold for 11 keys

Seller: https://backpack.tf/profiles/76561198067161406#!/compare/1532563200/1532736000

Buyer: https://backpack.tf/profiles/76561198166855771#!/compare/1532476800/1532563200

https://backpack.tf/item/6611813155

X = 11

Sale 3:

Sold for 9 keys

Seller: https://backpack.tf/profiles/76561198312583107#!/compare/1533427200/1533513600

Buyer: https://backpack.tf/profiles/76561198122595086#!/compare/1533254400/1533686400

https://backpack.tf/item/6993846273

X = 9

Sale 4:

Sold to a bot for 5 keys + 2 ref?

Seller: https://backpack.tf/profiles/76561198342696085#!/compare/1532044800/1533772800

Buyer: https://backpack.tf/profiles/76561198312583107#!/compare/1533254400/1533340800

Was 5 keys and 10 ref, according to bot.tf: https://i.imgur.com/F34S2Dz.png

https://backpack.tf/item/6993846273

X = 5?

No current sellers, apart from the ~$70 one on marketplace.tf

https://backpack.tf/item/6044373558

Sales at:

9

11

12

Even if the sale at 5 were correct, it’s a single sale to a quickbuyer, supported by several other quickbuyers at that price: https://i.imgur.com/BXXxW91.png - so 5 would be dropped anyways.

Going with 9-12.