Sale 1:

https://marketplace.tf/items/249;5;u86

$42.71 / $1.8 = 23.73 keys

Sale 2:

29 keys [ Excluding as high outlier ]

Sold for DBD Cadaver's Cranium(9 keys) + Mystery to everyone Smokey Sombrero(20 keys)

https://backpack.tf/profiles/76561198125791160#!/compare/1541548800/1541635200

https://backpack.tf/profiles/76561198073896407#!/compare/1541548800/1541635200

Cranium Mini: Unsold for 2 months at 9: https://imgur.com/a/bmpOXst

Sombrero Mini:

https://marketplace.tf/items/30682;5;u101

$30 / $1.77 = 16.95 keys

$37.99 / $1.8 = 21.11 keys

$40 / $1.77 = 22.60 keys

Average of these sales: 20.2 keys

Sale 3:

18 pure [ Excluding as less than key away from buyers: https://imgur.com/a/osNFVi4 ]

https://backpack.tf/profiles/76561198073896407#!/compare/1542240000/1542326400

https://backpack.tf/profiles/76561198344313987#!/compare/1542240000/1542326400

Sale 4:

20 keys

15 pure + Pro KS Minigun (5 keys) + 10 ref sweets

https://backpack.tf/profiles/76561198344313987#!/compare/1542585600/1542758400

https://backpack.tf/profiles/76561198031126990#!/compare/1542672000/1542844800

Minigun: https://imgur.com/a/eCxsfFb