Resuggesting this since the other guy didn't calculate for Unusual overpay and hasn't resubmitted his suggestion for a few hrs. This hat has more than 1 copy and both have changed hands at least once.

http://www.tf2outpost.com/trade/10831725 - Sold for a Cloudy Moon Waxy Wayfinder (11.8 Buds) and the Brain Slug owner added a Bud (Slug + Bud) altogether selling it at 10.8 Buds.

http://www.tf2outpost.com/trade/11341569 - Before that sale, it sold for a Time Warp Cold Killer (???) and a Bud (History shows that the Cold Killer was given to W4rI0!!! and the Brain Slug was given to MrDerpinBurger). http://www.tf2outpost.com/trade/11341569 - Just confirmed that he bought it for the Roboactive Slug + 1 Bud.

http://www.tf2outpost.com/trade/10886280 - The first sale, happening at a Burning AA (9.6 Buds) + a Bud (10.6 Buds altogether). The proof is here: http://www.tf2outpost.com/trade/10993770 (McDerpinBurger's comment, 4th reply to it).

http://www.tf2outpost.com/trade/11068671 - Offered a Burning Brain Slug + minor sweets (~8.7 Buds, and hello other suggester).

Conclusion: Altogether, past sales have happened around the high 10-bud range while people tend to offer below 10. Because of those 2 sales, I'm making the price 10.6-10.8. Feel free to provide counterproof if you find any.