Sale 1:

Sold for Potassium Bonnet (12)

http://www.tf2outpost.com/trade/29612484 - No B/O

Seller: https://backpack.tf/profiles/76561198341086501#!/compare/1523577600/1523664000

Buyer: https://backpack.tf/profiles/76561198255181725#!/compare/1523491200/1523664000

X = 12

Sale 2:

Sold for 10 keys (ID’s match)

Seller: https://backpack.tf/profiles/76561198344933095#!/compare/1522886400/1522972800

Buyer: https://backpack.tf/profiles/76561198382686347#!/compare/1521849600/1523404800

Bot.tf confirms: https://i.imgur.com/8Bl7MsX.png

X = 10

Sale 3:

Sold for Smoking Halogen Headlamp (Suggestion at 10)

No outpost

Seller: https://backpack.tf/profiles/76561198076479853#!/compare/1524787200/1525305600

Buyer: https://backpack.tf/profiles/76561198413309041#!/compare/1525046400/1525305600

X = 10

Sale 4:

Sold for Strange All-Father (~4.5)

Seller: https://backpack.tf/profiles/76561198105760264#!/compare/1523664000/1524009600

Buyer: https://backpack.tf/profiles/76561198132226518#!/compare/1523923200/1524009600

X = 4.5

Sale 5:

Bulk for DBD Physician’s Protector

Seller: https://backpack.tf/profiles/76561198316404854#!/compare/1524355200/1524441600

Buyer: https://backpack.tf/profiles/76561198226300264#!/compare/1523923200/1524355200

Sale 6:

Bulk for DBD Patriot Peak

Seller: https://backpack.tf/profiles/76561198114402400#!/compare/1524528000/1524614400

Buyer: https://backpack.tf/profiles/76561198074855595#!/compare/1524528000/1524614400

Smoking Halogen Headlamp:

https://backpack.tf/suggestion/5aedec8f44325a461a378478

Sellers:

9 keys:

https://i.imgur.com/ewRdmJD.png - cached, seller appears to be re-listing

https://backpack.tf/item/6517000233

~9.75 keys:

https://i.imgur.com/fWu3xth.png

https://backpack.tf/item/1659445013

https://backpack.tf/item/3037396467

https://backpack.tf/item/6681824966

Sales at:

10 (2x)

12

12 looks like a bit of an outlier, given all the cheaper sellers. Excluding 12.

Aged seller at 9 keys, using that as the low-end.

Going with 9-10.