Using last month

Sale 1:

Sold for 8 keys (ID’s match)

Seller: https://backpack.tf/profiles/76561198386441509#!/compare/1524873600/1524960000

Buyer: https://backpack.tf/profiles/76561198285277534#!/compare/1524960000/1525132800

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

X = 8

Sale 2:

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 3:

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 4:

Sold to a quickbuyer for 5 keys + 10 ref

Seller: https://backpack.tf/profiles/76561198190245951#!/compare/1524096000/1524960000

Buyer: https://backpack.tf/profiles/76561198011321852#!/compare/1524873600/1524960000

X = 5.5

Sale 5:

Quicksold for 5 keys + 20 ref

Seller: https://backpack.tf/profiles/76561198048851745#!/compare/1524787200/1524873600

Buyer: https://backpack.tf/profiles/76561198809718054#!/compare/1524787200/1524873600

X = 5.5

Sale 6:

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 7:

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 8:

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:

9 keys:

https://i.imgur.com/TAD6maY.png

https://backpack.tf/item/6538201739

https://backpack.tf/item/6291255838

10 keys:

https://i.imgur.com/E1MXvZv.png

https://backpack.tf/item/6252807010

https://backpack.tf/item/6434990574

12 keys:

https://i.imgur.com/wC9z7Ot.png

https://backpack.tf/item/6296884827

https://backpack.tf/item/6421485559

https://backpack.tf/item/6408638768

Sales at:

5 (2x)

5.5 (2x)

6

7

8

6 was excluded in my last attempt because there were quickbuyers at 6. These quickbuyers have dropped now, so I’ll include it in the range.

https://i.imgur.com/U1rKMnf.png - Quickbuyers at 5+ keys now, excluding 5.

Going with 6-8.