My first suggestion, I hope my proof is good enough. I think there are some sellers for under 2.4 keys and lots of unsold all-stars for 2.4 keys and higher. I bought mine gold painted for 2 keys + 1 ref.

Sellers for 2 keys:

http://www.tf2outpost.com/trade/12639047

http://www.tf2outpost.com/trade/12626113

http://www.tf2outpost.com/trade/12631901

http://www.tf2outpost.com/trade/12514161

http://www.tf2outpost.com/trade/11840884 (I think he wanna say 2 keys each)

Sellers/Unsold for more than 2 keys:

http://www.tf2outpost.com/trade/12597851 - 2.2 keys

http://www.tf2outpost.com/trade/12578219 - 2 keys + 2 ref.

http://www.tf2outpost.com/trade/12625491 - 12 ref.

http://www.tf2outpost.com/trade/12621594 - 2 keys + 0.66 ref.

http://www.tf2outpost.com/trade/12637820 - 2 keys + 2 ref.

http://www.tf2outpost.com/trade/12639071 - 2 keys + 0.66 ref.

http://www.tf2outpost.com/trade/12549360 - 2 keys + 2.33 ref.

http://www.tf2outpost.com/trade/12638429 - 2 keys + 2 ref (Australium Gold painted)

Unsold for more than 2 keys:

http://www.tf2outpost.com/trade/12443384 - 1 day

http://www.tf2outpost.com/trade/12503314 - 1 day (looks like he wants 2 keys + 2 ref.)

http://www.tf2outpost.com/trade/12559769 - 1 day

http://www.tf2outpost.com/trade/12504932 - 3 days

http://www.tf2outpost.com/trade/12437493 - 5 days

So that's it. Of course there are many other sellers, but they sell them painted or in a set or they have got low craft numbers. There are still many sellers at 3 keys, but I didn't see anyone selling them for that price, so it's not worth to list that, thanks.