Resubmitting based on feedback from last suggestion.

1-of-1 hat, recent sales:

First Usable Sale

https://backpack.tf/profiles/76561198120665449#!/compare/1467417600/1467849600 - Sold for Green Energy Tosslecap (87.5) + Max's (23) + 3 keys == ~113.5 keys

Rounding up to 114 keys.

Second sale is unusable due to being bulk with < 50% value, but it's here for reference:

https://backpack.tf/profiles/76561198095828101#!/compare/1467158400/1467244800 - Sold WITH an Eldritch Flame Pullover (140) + 3 keys:

Purple Energy Carouser's (31) + Duped Secret Drill Hat (120.5) + Orbiting Fire Yellow Belt (28) + Cloud 9 Soldered Sensei (34.5) + Duped Frostbite Guad (50) == ~264

264 - 143 == ~121 -- HOWEVER... Secret Drill Hat is also nearly a year out of date, plus with dupes and the 50% rule, makes it too messy to use.

Since we can't use that sale, but it's still a 1-of-1 hat that's not currently on the market, that gives us a usable pricing value of 114 keys.