I feel like this should have been updated forever ago but after having people say "oh I'm not willing to pay so much because backpack.tf" I've chosen to do something. Currently there are only 2 of these items for sale on outpost. My own, and playboys (http://backpack.tf/id/playboy1) the others are not for sale, and one is gifted. (accidentally hit enter, sorry)

Here is playboy's trade; http://www.tf2outpost.com/trade/7768544 which surprisingly doesn't have any real notable offers to encourage this range but then let's take a look at my trade.

http://www.tf2outpost.com/trade/6665647

We have quite a few notable offers includign a Vivid Noh Mercy (8.9-11.1) + Sunbeams Phantom (5.2-5.7) total of 14.1-16.8 (The noh sold for over 12 buds pure though, but that's still besides the point)

Then we have an offer of a Duped Vintage Big Kill, an Original Owner HOUWAR (11-12) + 3 Buds + 2 Buds in Spy Sweets which is a good 16-17 bud offer (made by http://steamcommunity.com/profiles/76561197996329849/)

All in all, I feel like this would be a much accurate range to say the least than the old 10-13 range.