Using last 2 months

Sales 1 & 2:

Sold for $19.99 and $15.95 on Marketplace.tf

https://marketplace.tf/items/1168;5;u3008

https://backpack.tf/item/5058622589 - $15.95 sale here, not sure if this is the $19.99 one as well

19.99/1.97 = ~10.15

15.95/1.97 = ~8.1

http://www.tf2outpost.com/trade/29586570 - B/O of 7 on the $15.95 sale

X = 10

X = 7 (capped by B/O)

Sale 3:

Sold for 7 keys + 19 ref

Seller: https://backpack.tf/profiles/76561198048851745#!/compare/1520035200/1520121600

Buyer: https://backpack.tf/profiles/76561198094046294#!/compare/1520035200/1520121600

X = 7.5

Sale 4:

Bulk for '72 Results

Seller: https://backpack.tf/profiles/76561198254375254#!/compare/1521763200/1522022400

Buyer: https://backpack.tf/profiles/76561198098805637#!/compare/1521936000/1522022400

Sellers:

~6.73 keys:

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

https://backpack.tf/item/6188443809

7 keys:

https://i.imgur.com/nW3MnVe.png

https://backpack.tf/item/6476735129

8 keys:

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

https://backpack.tf/item/5217422903

9 keys:

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

https://backpack.tf/item/6479437167

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

https://backpack.tf/item/6242042581

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

https://backpack.tf/item/5407379161

18 keys:

https://i.imgur.com/vuqSp9d.png

https://backpack.tf/item/4957394964

25 keys:

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

https://backpack.tf/item/4952983649

Sales at:

7

7.5

10

Ignoring the seller at ~6.7 keys as it's pretty young, and close enough to 7 anyways.

Going with 7-7.5