Proof:

http://www.tf2outpost.com/trade/14900460 - Sold for 5 in less than a day

http://www.tf2outpost.com/trade/14919304 - Sold for 5 in less than 9 hours

http://www.tf2outpost.com/trade/14920868 - Sold for 5 in less than 2 hours

http://www.tf2outpost.com/trade/14911143 - Sold for 5 in 1 hour

http://www.tf2outpost.com/trade/14907848 - Sold for 5 within a bump

http://www.tf2outpost.com/trade/14902373 - Sold for 5 within a bump

http://www.tf2outpost.com/trade/14921210 - Sold for 5.33 within an hour

http://www.tf2outpost.com/trade/14917776 - Sold for 5.33 within a bump

http://www.tf2outpost.com/trade/14893319 - Sold for 1 key in less than a day

http://www.tf2outpost.com/trade/14906001 - Sold for 1 key in less than a day

http://www.tf2outpost.com/trade/14900124 - Sold for 1 key in less than a day

http://www.tf2outpost.com/trade/14897482 - Sold for 1 key in less than a day

http://www.tf2outpost.com/trade/14893821 - Sold for 1 key in less than a day (same person as above, yet different GL)

http://www.tf2outpost.com/trade/14909900 - Sold 3 for 1 key? they're all in his backpack but he has many, possibly sold, not sure though

http://www.tf2outpost.com/trade/14750267 - Sold 1 for Quadwrangler (1) + 1 rec

At the moment of posting Classifieds had 1 at 5, 1 at 5.11, 1 at 5.22, 1 at 5.33 and rest at 1 key

Wide range but it seems very possible to sell at 1 key (6 ref) and some still sell for 5 so I leave it in range, and 5 became a quicksell so it needs a bump