I bought 8 of these a few months ago thinking that they would rise to 6 keys (for some reason). I ended up selling each of them for items (without much overpay) or quickselling them. I hate investing.

4.4 keys:

http://www.tf2outpost.com/trade/19557228 1 day

4.5 keys:

http://www.tf2outpost.com/trade/19521584 3 days

http://www.tf2outpost.com/trade/19466011 6 days

http://www.tf2outpost.com/trade/19540001 2 days (my trade)

http://www.tf2outpost.com/trade/19321921 14 days

http://www.tf2outpost.com/trade/19505209 4 days

http://www.tf2outpost.com/trade/19339563 Sold after nearly a week

http://www.tf2outpost.com/trade/19434743 Sold after a week

4.6 keys:

http://www.tf2outpost.com/trade/19543617 2 days

Unsold at 4.7 keys:

http://www.tf2outpost.com/trade/19559990 1 day

http://www.tf2outpost.com/trade/19571898 (about) 1 day

http://www.tf2outpost.com/trade/19478692 6 days

http://www.tf2outpost.com/trade/19557852 1 day

http://www.tf2outpost.com/trade/19558030 1 day

http://www.tf2outpost.com/trade/19514103 4 days

Unsold at 4.8 keys:

http://www.tf2outpost.com/trade/19552904 2 days

http://www.tf2outpost.com/trade/19573632 17 hours

Unsolds at 5 keys:

http://www.tf2outpost.com/trade/19552442 2 days

http://www.tf2outpost.com/trade/19561173 1 day

http://www.tf2outpost.com/trade/19472137 6 days

http://www.tf2outpost.com/trade/19462060 6 days

http://www.tf2outpost.com/trade/19547408 2 days

http://www.tf2outpost.com/trade/19434028 8 days

http://www.tf2outpost.com/trade/19561078 1 day

http://www.tf2outpost.com/trade/19506023 4 days

http://www.tf2outpost.com/trade/19193405 1 unsold 2 weeks, not too sure how long it took for the other one to sell

http://www.tf2outpost.com/trade/19492253 5 days

http://www.tf2outpost.com/trade/19438377 1 week

http://www.tf2outpost.com/trade/19462635 6 days

http://www.tf2outpost.com/trade/19345608 1 week

http://www.tf2outpost.com/trade/19521523 3 days

http://www.tf2outpost.com/trade/18628240 46 days

http://www.tf2outpost.com/trade/19463585 6 days

http://www.tf2outpost.com/trade/19128913 3 weeks

http://www.tf2outpost.com/trade/19481317 6 days

http://www.tf2outpost.com/trade/19503440 4 days

http://www.tf2outpost.com/trade/19570916 1 day

http://www.tf2outpost.com/trade/19505415 4 days

http://www.tf2outpost.com/trade/19367387 1 week

http://www.tf2outpost.com/trade/19473241 6 days

http://www.tf2outpost.com/trade/19424926 1 week

http://www.tf2outpost.com/trade/19303816 2 weeks

http://www.tf2outpost.com/trade/19526875 3 days

http://www.tf2outpost.com/trade/19328713 1 week

http://www.tf2outpost.com/trade/19396730 1 week

I think I've made my point with 5 keys not really selling.