Re-suggesting, using sales from the last suggestion onwards.

Sales 1-5:

Sold for $12.99, $12.56, $11.99 (2x), and $6 on marketplace.tf

https://marketplace.tf/items/30763;5;u3008

$6 is gonna be way too low, so I’ll exclude it.

12.99/1.98 = ~6.56

12.56/1.97 = ~6.38

11.99/1.9 = ~6.31

11.99/1.96 = ~6.12

X = 6.5 (3x)

X = 6

Sale 6:

Sold for 5 keys

Seller: https://backpack.tf/profiles/76561198312583107#!/compare/1531785600/1531872000

Buyer: https://backpack.tf/profiles/76561198140074467#!/compare/1531267200/1531872000

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

X = 5

Sale 7:

Sold for 4 keys + 18 ref

Seller: https://backpack.tf/profiles/76561198048851745#!/compare/1529884800/1529971200

Buyer: https://backpack.tf/profiles/76561197992294233#!/compare/1529884800/1529971200

X = 4.5

Sale 8:

Sold to a bot for 4 keys + 8 ref to a bot

Seller: https://backpack.tf/profiles/76561198162806285#!/compare/1529971200/1530057600

Buyer: https://backpack.tf/profiles/76561198312583107#!/compare/1529971200/1530057600

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

X = 4

Sale 9:

Bulk for pure

Seller: https://backpack.tf/profiles/76561198163912348#!/compare/1529884800/1529971200

Buyer: https://backpack.tf/profiles/76561198162806285#!/compare/1529884800/1529971200

There’s another bot.tf sale at 5 keys, but it’s untraceable to the point that the item’s history can’t be found:

https://backpack.tf/profiles/76561198334598690#!/compare/1530136800/1530223200

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

Sellers:

~5.45 keys:

https://i.imgur.com/mVXjAT3.png

https://backpack.tf/item/6267492582

12 keys:

https://i.imgur.com/mOc2sMb.png

https://backpack.tf/item/5277050790

Sales at:

4

4.5

5

6

6.5 (3x)

4 and 4.5 look low, excluding.

Going with 5-6.5.