decided to make a nicer suggestion (my old one was 85% accurate with a total of 239 votes)

sold for a MN bolted bird cage:

http://backpack.tf/item/2365939464 <--- hat history of the birdcage

http://backpack.tf/item/3319704614 <--- hat history of the bone dome

--- dates of last seen are both 1 day off, also it says unkown item, but if you check their outposts you can see he owned it

http://www.tf2outpost.com/trade/25731052

and

http://www.tf2outpost.com/trade/25699769

--- also both trades closed 1 day apart, "ironically"

11 x .9 = 9.9, rounding to 10 keys

i can't find another recent sale the other one on the market was traded 3+ months ago and the most recent sale for this one is all jumbled up from hyper-trading. also i havent found a single for this at 15 keys at all, even outdated sales, just a side note rlly ^_^ im guessing the other sold for around 10 keys http://www.tf2outpost.com/trade/25734262 (says that was his b/o in trade) and he now owns 9 untradeable keys, im assuming he spent one somehow, not going to use as proof, but more as supportive proof of this accurate price

better than my 8 key price suggestion lol, even though the both sold for that :p