I'm finally getting better at making suggestions! :D

SALE 1

https://marketplace.tf/items/tf2/31169;5;u172

$79.99/$2.1 = 38.1 Keys

SALE 2

https://backpack.tf/profiles/76561198171886670#!/compare/1609027200/1609113600

Sold for 29 Keys Pure from a bot

SALE 3

https://backpack.tf/profiles/76561198171487891#!/compare/1614470400/1616803200

Sold for 23.46 Keys from a bot also

SALE 4

https://backpack.tf/profiles/76561198197729211#!/compare/1621555200/1621728000

Bought for 20.40 Keys on a bot

Everything else I can find was either a clean history unbox or a complicated trade that included other items

Taking around 26 Keys based on the Median of all sales

I would really love to see suggestions or improvement comments as I want to suggest more items!