Updating 5 months old price. Only 8 such hats in existance, just 1 traded on OP, none in classifieds, on bazaar, tf2wh or tf2shop. Clearly almost no supply, but also very low demand. Some willing buyers for 13-14 keys, all rejected. One 15 key offer rejected, one considered, but retracted. Recent offer of items worth around 17 keys, C/O'ed, likely to be taken. One offer of 20 keys 2 months ago considered an outlier.

http://www.tf2outpost.com/trade/9575620

S: 3 weeks, B/O 25 keys

D: bubbling birdcage + sweets (around 17 keys), retracted; named, described s.f.flamethrower with 3 parts (around 17 keys), C/O'ed, willing to take

http://www.tf2outpost.com/trade/8330857

S: 2 months

D: 12-14 keys, rejected; B.M.O.C. + major sweets (13-14 keys), rejected; 14 keys, rejected; 15 keys, possibly retracted

http://www.tf2outpost.com/trade/8423295

D: colour-changing bill's + sweets (around 10 keys), rejected

http://www.tf2outpost.com/trade/7963880

S: 2 months, B/O 28 keys, sold for unknow price

D: 20 keys, rejected; B.M.O.C. + f.rocket launcher (around 15 keys), rejected