I sold one for 9.33 keys, which I bought a quicksell at 9.77 keys with.

https://backpack.tf/profiles/76561198188039146#!/compare/1500768000/1500854400

https://backpack.tf/profiles/76561198044195191#!/compare/1500595200/1500681600 - Sold for 10 Keys

https://backpack.tf/profiles/76561198209359071#!/compare/1499990400/1500076800 - Sold for a Pro KS Batsaber (~9 Keys) + ~1 Key of Items

https://backpack.tf/profiles/76561198118081118#!/compare/1498953600/1499126400 - Sold for ~12 Keys of Items

https://backpack.tf/profiles/76561198155268715#!/compare/1499040000/1499212800 - Sold for a Blizzardy Milkman (15.5 Keys)

15.5 is high because of Sellers, your sale at 9 is low because of the Buyers. I'd say go 10 - 12.

Thank you to Shuffle Spy for helping me gather these sells.