Using sales from April onwards.

Sale 1:

Sold for 10 keys (ID’s match)

Seller: https://backpack.tf/profiles/76561198272058312#!/compare/1524182400/1524355200

Buyer: https://backpack.tf/profiles/76561198005590158#!/compare/1524096000/1524268800

X = 10

Sale 2:

Sold for 9 keys + Uncraftable Ap-sap (~1)

Seller: https://backpack.tf/profiles/76561198110248446#!/compare/1522800000/1522972800

Buyer: https://backpack.tf/profiles/76561198248084520#!/compare/1521504000/1523059200

X = 10

Sale 3:

Sold for 8 keys

Seller: https://backpack.tf/profiles/76561198255644989#!/compare/1526083200/1526169600

Buyer: https://backpack.tf/profiles/76561198337235957#!/compare/1526083200/1526169600

X = 8

Sale 4:

Sold for $34.70 on Marketplace.tf

https://marketplace.tf/items/30845;5;u3004

Gonna be a large outlier, excluding.

Sale 5:

Sold with a couple keys in items for Miami Nights Airdog

Seller: https://backpack.tf/profiles/76561198248084520#!/compare/1523750400/1523836800

Buyer: https://backpack.tf/profiles/76561198272058312#!/compare/1523664000/1523750400

Better off being used on the Airdog.

Sellers:

9 keys:

https://i.imgur.com/SfXLOi6.png

https://backpack.tf/item/6311141684

10 keys:

https://i.imgur.com/hxMV8Bo.png

https://backpack.tf/item/6252774052

12 keys:

https://i.imgur.com/6W0Jwoz.png

https://backpack.tf/item/6577668130

15 keys:

https://i.imgur.com/2C0krwf.png

https://backpack.tf/item/6409571749

20 keys:

https://i.imgur.com/QFMo2CO.png

https://backpack.tf/item/6253824604

Sales at:

8

10 (2x)

Going with 8-10.