You can't hold back when you got the whip.

Selling between 4.5 and 4.3 keys

http://www.tf2outpost.com/trade/14920344 - 4.5

http://www.tf2outpost.com/trade/14918454 - 4.5

http://www.tf2outpost.com/trade/14939113 - 4.5

http://www.tf2outpost.com/trade/14950613 - 4.4

http://www.tf2outpost.com/trade/14892941 - 4.3

http://www.tf2outpost.com/trade/14853320 - has offers between 4 and 4.5 keys

Selling for less than 4.3

http://www.tf2outpost.com/trade/14945765 - 4.17 (4 keys 1 ref)

SOLD:

http://www.tf2outpost.com/trade/14944952 - 4 keys

http://www.tf2outpost.com/trade/14936444 - 4 keys

http://tf2tp.com/trade.php?trade=9827129 - 3.5? maybe?

http://www.tf2outpost.com/trade/14931648 - 4.5

http://www.tf2outpost.com/trade/14927898 - 4.11

http://www.tf2outpost.com/trade/14923313 - 3 keys ;-;

http://www.tf2outpost.com/trade/14910129 - 4.5

http://www.tf2outpost.com/trade/14910125 - 4

http://backpack.tf/classifieds/search/id/521d757fba2536856d8b4567 - look at all those whips at 4.5

Conclusion: Anything less than 4.3 is quicksell, 4.5 moves slowly. I guess the market is shifting towards 4 keys in the near future.