Sale #1 -

https://marketplace.tf/items/tf2/31002;5;u10

https://backpack.tf/item/7329425303

$43.99 / $1.81 = 24.30 keys

https://bot.tf/stats/listings/4JGZE029 b/o was 24

Sale #2 -

https://backpack.tf/profiles/76561198087511120#!/compare/1566518400/1566950400

https://backpack.tf/profiles/76561198263360913#!/compare/1566864000/1566950400

18 pure (Histories dont match because original was sold to bot before tank top was bought)

Sale #3 -

https://backpack.tf/profiles/76561198263360913#!/compare/1568419200/1568505600

https://backpack.tf/profiles/76561198342161127#!/compare/1568419200/1568505600

With adds for burning head hedge, stuntman most likely involved, but if not would be a high outlier anyway

Sale #4 -

https://backpack.tf/profiles/76561197970869719#!/compare/1571529600/1571616000

https://backpack.tf/profiles/76561198089253101#!/compare/1571529600/1571616000

Bulk

Nothing really shows 24 is high, + it was fairly recent, so going with 18-24

Sellers - https://imgur.com/a/CMO2oUR

2 mths @25, 15 days at 23