Sale 1:

Sold for 5 keys + ~2 keys in metal/items

Seller: https://backpack.tf/profiles/76561198048851745#!/compare/1524268800/1524355200

Buyer: https://backpack.tf/profiles/76561198066105037#!/compare/1524268800/1524355200

X = 7

Sale 2:

Sold for 6 keys

Seller: https://backpack.tf/profiles/76561198143229539#!/compare/1523232000/1524009600

Buyer: https://backpack.tf/profiles/76561198126985704#!/compare/1523923200/1524009600

X = 6

Sale 3:

Sold for $10 on Marketplace.tf

https://marketplace.tf/items/1183;5;u3008

Can’t find item’s history

10/1.97 = ~5.08

X = 5

Sale 4:

Sold for 5 keys

Seller: https://backpack.tf/profiles/76561198079883481#!/compare/1520726400/1523404800

Buyer: https://backpack.tf/profiles/76561198119563409#!/compare/1523404800/1523491200

X = 5

Sale 5:

Sold for 5 keys

Seller: https://backpack.tf/profiles/76561198072898758#!/compare/1522800000/1523232000

Buyer: https://backpack.tf/profiles/76561198432068902#!/compare/1522800000/1522886400

X = 5

Sale 6:

Sold for Orbiting Fire Airdog

No outpost

Seller: https://backpack.tf/profiles/76561198286689467#!/compare/1523059200/1523145600

Buyer: https://backpack.tf/profiles/76561198253395553#!/compare/1523059200/1523145600

Gonna be a large outlier, excluding.

Sellers:

7 keys:

https://i.imgur.com/mCe8rtG.png

https://backpack.tf/item/6287205832

8 keys:

https://i.imgur.com/qoeE4YF.png

https://backpack.tf/item/6342610562

9 keys:

https://i.imgur.com/hOk5V8K.png

https://backpack.tf/item/6408638768

10 keys:

https://i.imgur.com/8kqe1uG.png

https://backpack.tf/item/6252807010

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

https://backpack.tf/item/6434990574

12 keys:

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

https://backpack.tf/item/6296884827

18 keys:

https://i.imgur.com/W7hAuS0.png

https://backpack.tf/item/6291255838

Sales at:

5 (3x)

6

7

Quickbuyers at 6+ keys

https://i.imgur.com/inwAj4B.png

Excluding 5 and 6.

Going with 7 flat.

Bulk for abduction phononaut

https://backpack.tf/profiles/76561198126985704#!/compare/1524182400/1524268800

https://backpack.tf/profiles/76561198093528879#!/compare/1524268800/1524873600

Looks like the seller at 8 keys sold. I'll re-suggest when i wake up tomorrow.