Sales 1-3:

Sold for $16.45 & $16.85 (2x) on marketplace.tf.

https://marketplace.tf/items/30616;5;u3005

16.85/1.96 = ~8.6

16.85/1.97 = ~8.55

16.45/1.94 = ~8.48

X = 8.5 (3x)

Sale 4:

Sold with ~0.5 keys in items for ’72 Stagger (Suggestion at 6.5)

Seller: https://backpack.tf/profiles/76561198279985917#!/compare/1532476800/1532563200

Buyer: https://backpack.tf/profiles/76561198060319763#!/compare/1532476800/1532563200

X = 6

Sale 5:

Sold for 5 keys to a likely quickbuyer

Seller: https://backpack.tf/profiles/76561198097002664#!/compare/1531785600/1531872000

Buyer: https://backpack.tf/profiles/76561198203307876#!/compare/1531785600/1531872000

X = 5

Sellers:

~9.55 keys:

https://i.imgur.com/vR1n5rM.png

https://backpack.tf/item/4982179329

13 keys:

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

https://backpack.tf/item/3976968072

20 keys:

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

https://backpack.tf/item/5498719079

http://www.tf2outpost.com/trade/29722740

Offers:

http://www.tf2outpost.com/trade/29634894

Sales at:

5

6

8.5 (3x)

5 is an outlier, excluding.

Going with 6-8.5.