Sale 1:

Sold for 10 keys

Seller: https://backpack.tf/profiles/76561198154211785#!/compare/1526774400/1526860800

Buyer: https://backpack.tf/profiles/76561198089808211#!/compare/1526774400/1526860800

https://backpack.tf/item/1021465387

X = 10

Sales 2 & 3:

Sold for $18 and $14 on marketplace.tf

https://marketplace.tf/items/613;5;u36

https://backpack.tf/item/621969212 (might be the history for both)

http://manicbot.me/keyprice/?at=2018-08-12

18/1.89 = ~9.52 keys

http://manicbot.me/keyprice/?at=2018-08-13

14/1.89 = ~7.41 keys

X = 9.5

X = 7.5

Sale 4:

Sold for 8 keys + 4 ref

Seller: https://backpack.tf/profiles/76561198304138933#!/compare/1527897600/1527984000

Buyer: https://backpack.tf/profiles/76561198200802299#!/compare/1527897600/1527984000

Untraceable. Bot.tf confirms, but it is unreliable. Item histories below:

https://backpack.tf/item/1326825842 - Gym Rat

https://backpack.tf/item/6893887256 - keys

https://backpack.tf/item/6893887273

https://backpack.tf/item/6893887288

https://backpack.tf/item/6893887293

https://backpack.tf/item/6893887297

https://backpack.tf/item/6893887304

https://backpack.tf/item/6893887315

https://backpack.tf/item/6893887323

https://backpack.tf/item/6893887331 - ref

https://backpack.tf/item/6893887340

https://backpack.tf/item/6893887343

https://backpack.tf/item/6893887348

X = 8

Sale 5:

Sold to a bot for 7 keys + 12 ref?

Seller: https://backpack.tf/profiles/76561198066009371#!/compare/1527724800/1527984000

Buyer: https://backpack.tf/profiles/76561198304138933#!/compare/1527897600/1527984000

12 ref matches, but keys aren’t visible. That being said, I doubt the sale is incorrect. Bot.tf confirms: https://i.imgur.com/p3XZqAx.png

https://backpack.tf/item/1326825842

X = 7.5

Sale 6:

Sold to a bot for 7 keys + 12 ref?

Seller: https://backpack.tf/profiles/76561198143715421#!/compare/1529107200/1529193600

Buyer: https://backpack.tf/profiles/76561198304138933#!/compare/1529107200/1529193600

12 ref matches, just like Sale 5. Treating it similarly. https://i.imgur.com/p3XZqAx.png

https://backpack.tf/item/718405140

X = 7.5

Sale 7:

Sold for ’72 Meet the Medic (6)

No outpost

Seller: https://backpack.tf/profiles/76561198062365679#!/compare/1527897600/1527984000

Buyer: https://backpack.tf/profiles/76561198356853241#!/compare/1527897600/1527984000

https://backpack.tf/item/1326825842

X = 6

Sale 8:

Bulk for Hot FT Pizza Polished War Paint

Seller: https://backpack.tf/profiles/76561198142244035#!/compare/1526601600/1526688000

Buyer: https://backpack.tf/profiles/76561198154211785#!/compare/1526601600/1526688000

https://backpack.tf/item/1021465387

Sellers:

https://i.imgur.com/plcDT0V.png

~8.5 keys:

https://backpack.tf/item/6190951683

9 keys:

https://backpack.tf/item/621969212

Sales at:

6

7.5 (3x)

8

9.5

10

On top of what we have, there are apparently 2 more sales at ~8 keys, according to bot.tf: https://i.imgur.com/p3XZqAx.png

https://backpack.tf/item/1326825842

https://backpack.tf/item/718405140

With all the sales and sellers at around that price in mind, it should be safe to exclude the sales at 9.5 and 10. Especially since the pure sale at 10 is almost too old to use now.

6 is an outlier, excluding 6.

Going with 7.5-8.