These just aren't being sold for 5 keys. Most that are being sold are traded at 6 keys, and some sellers are asking for (but not getting) more.

Those selling/sold at 6 keys:

http://www.tf2outpost.com/trade/6880978- Sold for 6 keys

http://www.tf2outpost.com/trade/6840513 - Selling for 6 keys

http://www.tf2outpost.com/trade/6662975 - Sold several for 6 keys

http://www.tf2outpost.com/trade/6849889 - Selling for 6 keys

http://www.tf2outpost.com/trade/5153778 - Selling for 6 keys

This is the only one I could wind with a five where the keys are, and this is what makes the range 5.5 - 6. And before anyone comments about it being unsold, the trade has only been up for 2 days, and the demand for mid-high tier vintages is practically nonexistent - it may take longer than normal stranges to sell.

http://www.tf2outpost.com/trade/6838716 - Selling for 5 keys + 1 ref

I am making this suggestion because the current price is inaccurate. If no-one is willing to sell at 5 keys, then it's highly unlikely that any have sold at 5 keys.

And for once guys, don't be mystery down voters. On almost all my suggestions there are ~5 people who down vote without posting a comment. If you have a valid reason why this shouldn't go through, tell me! Others can follow your lead - if you're right.

Let me know what you think :D