Using last month.

Sales 1-3:

Sold for $20, $17.75 and $15 on marketplace.tf

https://marketplace.tf/items/30673;5;u3007

20/1.97 = ~10.2

17.75/1.97 = ~9.01

15/1.97 = ~7.61

X = 10

X = 9

X = 7.5

Sale 4:

Sold for 7 keys

Seller: https://backpack.tf/profiles/76561198334598690#!/compare/1526169600/1526256000

Buyer: https://backpack.tf/profiles/76561198177822454#!/compare/1526083200/1526256000

Bot.tf confirms: https://i.imgur.com/tTTkfo7.png

Key histories:

https://backpack.tf/item/6371170049

https://backpack.tf/item/4661231044

https://backpack.tf/item/4664314055

https://backpack.tf/item/6629726611

https://backpack.tf/item/6689206511

https://backpack.tf/item/997340373

https://backpack.tf/item/6054098084

(In case the compare link changes)

X = 7

Sale 5:

Sold for 5 keys

Seller: https://backpack.tf/profiles/76561198048479665#!/compare/1525046400/1525132800

Buyer: https://backpack.tf/profiles/76561198398063696#!/compare/1524960000/1525046400

X = 5

Sale 6:

Sold for 5 keys in a trade hold (buyer’s compare link). Took ~2 days.

Seller: https://backpack.tf/profiles/76561198121830870#!/compare/1524614400/1524960000

Buyer: https://backpack.tf/profiles/76561198117379982#!/compare/1524700800/1524960000

X = 5

Sale 7:

Sold with a key + flamethrower fabricator (~1) for Strange Festivized Scattergun (~0.5)

Seller: https://backpack.tf/profiles/76561198202796064#!/compare/1524528000/1524614400

Buyer: https://backpack.tf/profiles/76561198177393451#!/compare/1524528000/1524614400

X = -1.5

Sale 8:

Sold for Holy Grail Headcase + 3 keys

No outpost

Seller: https://backpack.tf/profiles/76561198063640894#!/compare/1524355200/1524441600

Buyer: https://backpack.tf/profiles/76561198328947519#!/compare/1524441600/1524787200

Not using without a B/O.

Sale 9:

Sold for Spelled Killer Exclusive

Seller: https://backpack.tf/profiles/76561198165100402#!/compare/1524787200/1524873600

Buyer: https://backpack.tf/profiles/76561198103373853#!/compare/1524787200/1524873600

Not touching this one.

Sellers:

~7 keys:

https://i.imgur.com/p9LM4oK.png

https://backpack.tf/item/4388559905

12 keys:

https://i.imgur.com/UqXPr9j.png

https://backpack.tf/item/5374386942

29 keys:

https://i.imgur.com/zGjz9v5.png

https://backpack.tf/item/6680269166

40 keys:

https://i.imgur.com/tAbx9hW.png

https://backpack.tf/item/4444098024

Sales at:

-1.5

5 (2x)

7

7.5

9

10

Seller at 7 frequently re-lists their items. Should be safe to assume that their B/O has been 7 for longer than displayed. With this in mind, we shouldn’t stray too high above this seller. Excluding 9 and 10.

Not comfortable having 5 in the range, as it was quickbuyer price not too long ago: https://i.imgur.com/XnCQNLf.png

Excluding 5 would also balance out the exclusion of the sales at 9 and 10.

Going with 7-7.5.