Proof:

Sales at 4.33 and above:

http://imgur.com/YcCkGMH - 1 at 4.33, 1 at 6

http://imgur.com/3yY0Vyy - 1 at 4.66, 1 at 5

http://imgur.com/AAWw8XP - 1 at 5, 1 at 6

http://www.tf2outpost.com/trade/18895256 - 4.33 ref, less than an hour

http://www.tf2outpost.com/trade/18897763 - 4.33 ref, without a bump

http://www.tf2outpost.com/trade/18874274 - 5 ref, less than 19 hours

http://www.tf2outpost.com/trade/18875019 - 5 ref, less 11 hours

http://www.tf2outpost.com/trade/18899064 - 5 ref, less than 9 hours

http://www.tf2outpost.com/trade/18855682 - 2 for 5 ref, less than a day

http://www.tf2outpost.com/trade/18859244 - 1 key, without a bump

I leave 4.33 at range because I found more sales at it, even some at 4 so quicksell or not, it's a common price

I think 5 should be high end because there are multiple sales at it and lets be honest, it's basically a quicksell already