Let's try again. Last suggestion might have been a little high, so I've decreased the price slightly. Here's some proof:

http://www.tf2outpost.com/trade/8682903

Buyout: 1 bud

Offers:

• 14 keys (rejected)

http://www.tf2outpost.com/trade/8156564

Buyout: 1 bud

Offers:

• s.f.huntsman (13 keys)

• steaming pencil pusher (19-21 keys)

http://www.tf2outpost.com/trade/8742749

Buyout: 1 bud

Offers:

• blizz geisha boy (25-31 keys, kind of old price) + sweets

http://www.tf2outpost.com/trade/8384110

Buyout: 20 keys, sold for unknown amount

http://www.tf2outpost.com/trade/8178110

SOLD 3 weeks ago

BO was 15 keys, but someone offered 16

http://www.tf2outpost.com/trade/8331366

SOLD 2 weeks ago

Sale price: big kill (15-16 keys)

http://www.tf2outpost.com/item/440/1457538818/161/6

http://www.tf2outpost.com/trade/8059054

SOLD 1 week ago

Sale price: 20 keys

http://www.tf2outpost.com/trade/8040519

SOLD 1 month ago

Sale price: 2x black bills

http://www.tf2outpost.com/item/440/1408898360/126/6

http://www.tf2outpost.com/item/440/1408898358/126/6 <-- gifted

http://www.tf2outpost.com/trade/7112396

SOLD 2 months ago

Unknown sale price, BO was 22 keys

http://www.tf2outpost.com/trade/7720599

SOLD 1 month ago

BO price was 18 keys

http://www.tf2outpost.com/trade/7758567

SOLD 1 month ago

BO price was 23 keys

Conclusion: While it might not seem like much, the sales of this hat vary from 15 keys to 23 keys. However, 5 of them sold for more than 16 keys, while one sold for 15 and one for 16, so a low value of 17 keys is appropriate. Since there was a month old sale at 23 keys, and link three was offered a blizz geisha boy (kind of old price, a couple of BOs at 25 keys), I'll drop the high end by a little bit, and center it around 20 keys. Let me know what you think~