Counter to the other suggestion.

0.9=5.33 ref

http://backpack.tf/classifieds/search/id/52573fb24cd7b86f5c8b4567

Currently none available for less than 5.33.

From his own "unsolds/solds below price" proof;

4.66

http://www.tf2outpost.com/trade/15098513 - Sold (on first day)

http://www.tf2outpost.com/trade/15148729 - Instasold

5 ref

http://www.tf2outpost.com/trade/15221418 - Instasold

http://www.tf2outpost.com/trade/15172140 - Instasold

http://www.tf2outpost.com/trade/15210789 - Instasold

http://bazaar.tf/trade/498062 - Instasold

http://www.tf2outpost.com/trade/15217038 - Instasold

http://www.tf2outpost.com/trade/15207044 - Instasold (left open)

http://www.tf2outpost.com/trade/15211647 - Instasold (also left open)

5.33

http://www.tf2outpost.com/trade/15220650 - Sold within an hour

http://www.tf2outpost.com/trade/15223216 - (legitmately unsold)

http://www.tf2outpost.com/trade/15213995 - Instasold

http://bazaar.tf/trade/498616 - Instasold

http://www.tf2outpost.com/trade/15218094 - Instasold

http://www.tf2outpost.com/trade/15221072 - Instasold

http://www.tf2outpost.com/trade/15128760 - Instasold

5.66

http://www.tf2outpost.com/trade/15195347 - Instasold

http://tf2tp.com/trade.php?trade=9852548 - Sold on first day.

And 1 key is still possible:

http://tf2tp.com/trade.php?trade=9854035

http://www.tf2outpost.com/trade/15241192

http://www.tf2outpost.com/trade/15241064

http://www.tf2outpost.com/trade/15241062

http://www.tf2outpost.com/trade/15240939

http://tf2tp.com/trade.php?trade=9854042

http://www.tf2outpost.com/trade/15241725

http://www.tf2outpost.com/trade/15244018

http://tf2tp.com/trade.php?trade=9854254

http://www.tf2outpost.com/trade/15247382

http://www.tf2outpost.com/trade/15249175

http://www.tf2outpost.com/trade/15248886

http://www.tf2outpost.com/trade/15248961

http://www.tf2outpost.com/trade/15250025

http://www.tf2outpost.com/trade/15249305

http://www.tf2outpost.com/trade/15251582

http://www.tf2outpost.com/trade/15251582

http://www.tf2outpost.com/trade/15252429

http://www.tf2outpost.com/trade/15257475

http://www.tf2outpost.com/trade/15257785

i.e. 5 ref is a quicksell and shouldn't be in range/1 key is still possible