Resuggestion.

Thanks to FishCrimes for the info!

Sale 1:

https://backpack.tf/profiles/76561198048851745#!/compare/1525996800/1526083200

https://backpack.tf/profiles/76561198175367966#!/compare/1525996800/1526083200

https://imgur.com/gallery/6bAl1R4

Sold for 8 keys + 10 ref

Sale 2:

https://backpack.tf/profiles/76561198175367966#!/compare/1526083200/1526169600

https://backpack.tf/profiles/76561198008720570#!/compare/1526083200/1526169600

Sold for 9 keys

Sale 3:

https://backpack.tf/profiles/76561198008720570#!/compare/1526860800/1527033600

https://backpack.tf/profiles/76561198121830870#!/compare/1526947200/1527033600

Sold for 7 keys

Sale 4:

https://backpack.tf/profiles/76561198121830870#!/compare/1526947200/1527033600

https://backpack.tf/profiles/76561198108020471#!/compare/1526947200/1527033600

Untraceable.

Sale 5:

https://backpack.tf/profiles/76561198108020471#!/compare/1527379200/1527465600

Bulk.

Total sales @:

7, 8.31, 9

Buyers up to 7.19

Going with 8.5 to 9 keys.

FishCrimes' Part:

-Sold for ~7 keys: https://backpack.tf/profiles/76561198819336705#!/compare/1531872000/1531958400 https://backpack.tf/profiles/76561198819336705#!/compare/1531872000/1531958400 https://webcache.googleusercontent.com/search?q=cache:rDm5qAfmSRMJ:https://backpack.tf/stats/Unusual/A%2520Head%2520Full%2520of%2520Hot%2520Air/Tradable/Craftable/36+&cd=3&hl=en&ct=clnk&gl=us https://i.gyazo.com/4c20c25de3e68690269e01cccf837adf.mp4

-New unsold at 8: https://i.gyazo.com/6f205c8f837ae1681c01ffe57ff133c4.mp4

Half of the data we now have for this hat (2/4 sales) are now ~7 keys. I would make this 7-9.