Sale 1:

Sold for ~7 keys in items

No outpost

Seller: https://backpack.tf/profiles/76561198804077112#!/compare/1522627200/1522713600

Buyer: https://backpack.tf/profiles/76561198384937944#!/compare/1522627200/1522713600

X = 7

Sale 2:

Sold for 5 keys + ~1.5 keys in items

No outpost

Seller: https://backpack.tf/profiles/76561198155545034#!/compare/1521331200/1521417600

Buyer: https://backpack.tf/profiles/76561198346875595#!/compare/1521331200/1521417600

X = 6.5

Sale 3:

Sold for 4 keys + ~2.5 keys in items

No outpost

Seller: https://backpack.tf/profiles/76561198346875595#!/compare/1521417600/1521763200

Buyer: https://backpack.tf/profiles/76561198143320939#!/compare/1521417600/1521504000

X = 6.5

Sale 4:

Sold for 6 keys

Seller: https://backpack.tf/profiles/76561198024867201#!/compare/1522972800/1523059200

Buyer: https://backpack.tf/profiles/76561198100128947#!/compare/1523059200/1523232000

X = 6

Sale 5:

Sold for 6 keys + 2 ref to a bot

Seller: https://backpack.tf/profiles/76561198083577402#!/compare/1521763200/1521849600

Buyer: https://backpack.tf/profiles/76561198308819102#!/compare/1521763200/1521849600

Bot.tf confirms: https://i.imgur.com/c66DAK1.png

X = 6

Sale 6:

Sold to a quickbuyer for 5 keys

Seller: https://backpack.tf/profiles/76561198118702880#!/compare/1521936000/1522022400

Buyer: https://backpack.tf/profiles/76561198048851745#!/compare/1521936000/1522540800

X = 5

Sale 7:

Bulk for Bubbling Timeless Topper

Seller: https://backpack.tf/profiles/76561198143320939#!/compare/1521417600/1521504000

Buyer: https://backpack.tf/profiles/76561198157926451#!/compare/1521417600/1521504000

Sale 8:

Bulk for Cloud 9 Towering Pillar of Hats

Seller: https://backpack.tf/profiles/76561198414948037#!/compare/1522627200/1522713600

Buyer: https://backpack.tf/profiles/76561198804077112#!/compare/1522454400/1522627200

Sellers:

~6 keys:

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

https://backpack.tf/item/5611662667

~7.85 keys:

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

https://backpack.tf/item/6523694615

9 keys:

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

https://backpack.tf/item/3062812283

Sales at:

5

6 (2x)

6.5 (2x)

7

5 went to a quickbuyer, excluding.

Going with 6-7.