Not sure if I'd even want to use that sale here.

https://backpack.tf/profiles/76561198152434713#!/compare/1527811200/1527897600

https://backpack.tf/profiles/76561198342161127#!/compare/1527811200/1527897600

The person who apparently paid 31 keys dumped it on another quickbuyer below the price he got the hat for, after just 1 day of when buying it. This makes me think it was either just a poor trading decision and thus the sale does not accurately represent the market here, or just burning pure. In which case my reasons provided why this sale isn't accurate, are still valid.

However,

https://marketplace.tf/items/30546;5;u33

Sold for $60 ( / $1,96 ) = ~31 keys.

https://backpack.tf/profiles/76561197999139658#!/compare/1525478400/1525651200

https://backpack.tf/profiles/76561198388952441#!/compare/1525478400/1525564800

Sale 1 seems to have been gambled.

More sales:

https://backpack.tf/item/6824206272

Scrap.tf sales.

https://marketplace.tf/items/30546;5;u33

$44, roughly 22 keys. Low.

https://marketplace.tf/items/30546;5;u33

Sold for $112, which is ~57-58 keys. This is way too high considering there's 2 sellers at 33 / 50 keys and a ton of sales below 57-58 keys.

https://backpack.tf/profiles/76561198286257338#!/compare/1526688000/1526774400

https://backpack.tf/profiles/76561198049149130#!/compare/1526688000/1526774400

Sold for 26 keys.

Your second sale appears to be ~27 keys. Which means sales here are at 26 / 27 / 31 / (31) and a whole bunch of scrap sales, low marketplace sales etc that support a range here. Would probably go with 26-31 keys.