Sale 1:

Sold for $23.99 on Marketplace.tf

https://marketplace.tf/items/104;5;u35

Couldn't identify history.

23.99/2.03 = ~11.8

X = 12

Sale 2:

Sold for $20 on Marketplace.tf

https://marketplace.tf/items/104;5;u35

https://backpack.tf/item/637513842

20/2.05 = ~9.75

X = 10

Sale 3:

Sold for 8 keys + ~2 keys in items

Seller: https://backpack.tf/profiles/76561198023051867#!/compare/1496016000/1496102400

Buyer: https://backpack.tf/profiles/76561198309442483#!/compare/1496016000/1496102400

X = 10

Sale 4:

Sold for Steaming Hetman's (10.5) in ~2 days

http://www.tf2outpost.com/trade/29230349 - B/O of ~8.7

Seller: https://backpack.tf/profiles/76561198345783002#!/compare/1497571200/1497657600

Buyer: https://backpack.tf/profiles/76561198065049657#!/compare/1497484800/1497571200

X = 9 (Capped by B/O, rounded)

Sale 5:

Quicksold for 8 keys + <0.5 keys in metal/items

Seller: https://backpack.tf/profiles/76561198263344996#!/compare/1497139200/1497398400

Buyer: https://backpack.tf/profiles/76561198345783002#!/compare/1497312000/1497398400

X = 8

Sale 6:

Bulk for Terror-Watt Killer Exclusive

Seller: https://backpack.tf/profiles/76561198118254940#!/compare/1497312000/1497398400

Buyer: https://backpack.tf/profiles/76561198263344996#!/compare/1497139200/1497398400

Sellers:

10 keys:

http://i.imgur.com/U1p9eMk.png - 10 days

http://www.tf2outpost.com/trade/29327626

11 keys:

http://i.imgur.com/PSDZNXN.png - 5 days

Sales at:

12

10 (2x)

9

8

12 looks like an outlier, given the sales and sellers for cheaper. Excluding 12.

8 quicksold, excluding 8.

Going to exclude 9 as well, due to it selling in a short amount of time, for much more than the B/O. The Hetmans involved in that sale has a seller at ~9.5, and several sellers for less than 11 keys, as well as a 2 month old seller at 11, so it should be fine to value the sale at ~10 keys, if we were to exclude the B/O cap here.

Going with 10 flat.