Furthermore, those that sell at 4 ref or higher seem to consist of pure luck and a lot of waiting time. More links:

Selling for 4 ref / 1.5 keys: http://www.tf2outpost.com/trade/5753946

http://www.tf2outpost.com/trade/5789370

http://www.tf2outpost.com/trade/5290229

http://www.tf2outpost.com/trade/5739254

Buying regularly/bought at a key: http://www.tf2outpost.com/trade/4437557

http://www.tf2outpost.com/search/46251854

http://www.tf2outpost.com/trade/4972749

http://www.tf2outpost.com/trade/5154870

http://www.tf2outpost.com/trade/4912534

Buying/bought at 3 ref:

http://www.tf2outpost.com/trade/5470666

http://www.tf2outpost.com/trade/5325920

The warehouse has v. Loch and Loads selling at 14,220 each which is about 1 key + 0.77 and buying at 13,650 which is about 1 key + 0.55 and they are overstocked 24/7