This is my first unusual suggestion, please offer feedback when I inevitably mess something up.

I really like this hat, but apparently I am alone when it comes to demand

This is the only one I know of which has been traded:

https://backpack.tf/item/5929038981

There are two usable sales, both were for pure

Sale 1: May 18th (2 months ago)

I bought this hat for 9 keys and 38.55 ref on May 18th - rounding to 9.5 keys

https://backpack.tf/profiles/76561198027853812#!/compare/1589673600/1589846400

Sale 2:

I sold this hat for 10 keys on June 28th - 10 keys

https://backpack.tf/profiles/76561198027853812#!/compare/1592956800/1593302400

Sale 3: Scammed from the person I sold it to, not using

Conclusion:

2 usable sales: 9.5 keys and 10 keys

there is another sale (the person I bought it from) but that was more than 2 months ago (so it will not be included)

Final range: 9.5 - 10

I think that is it.