Credit to Mindacos

Sold for $16 and $26.40 on Marketplace(~8 Keys using 1.95 value and ~13 using 1.96 value). Both sales are outliers.

https://marketplace.tf/items/30807;5;u107

Sold for 10 Keys

https://backpack.tf/profiles/76561198107120524#!/compare/1511222400/1511481600

Sold for ~9.7 Keys in Metal, round to 10

https://backpack.tf/profiles/76561198051616613#!/compare/1507680000/1507766400

Sold for a Steaming Demoman's Fro(11 Keys)*

https://backpack.tf/profiles/76561198051616613#!/compare/1507593600/1507680000

*The Festive Flame Thrower that was added was 10 Refined at the time, which means that this rounds down to 11.

Sold for ~11 Keys in Items

https://backpack.tf/profiles/76561198068697477#!/compare/1512259200/1512432000

Sold for 9 Keys

https://backpack.tf/profiles/76561197963500354#!/compare/1509235200/1509321600

Sold for ~8.5 Keys, round to 9

https://backpack.tf/profiles/76561198219902779#!/compare/1510444800/1510531200

Sold for 10 Keys

https://backpack.tf/profiles/76561198005125928#!/compare/1510531200/1510876800

Sold for a Terror-Watt Bloke's Bucket Hat(10.5 Keys)

https://backpack.tf/profiles/76561198005032783#!/compare/1504828800/1504915200

9-11.