You got 1, rather old sold. And why would you include 15 in the range if 14 doesn't sell easily?

Downvote, sorry.

Fair enough of a suggestion. I do think that collectors can request any price for their weapons. Since there aren't many sellers around, they can set their own prices (here 14 keys being one). Although 15 keys shouldn't be in range definitely. Still, upvoted.

There are more trades here

http://www.tf2outpost.com/trade/18969546

http://www.tf2outpost.com/trade/18789886 - bought for 6

There is also no complete sale at 15 keys. You'll need proof of a sale to include that in the range