Firstly, there's an unfunny amount of people trying to sell for 3+ keys. Nearly all the sellers on outpost ask 3 or more. They don't get them. HOWEVER, since people are offering 2 keys on this, and There's even a person with a buying trade for 2 keys apiece, I suggest a push upward.

http://www.tf2outpost.com/trade/7265881 Rejected a lower offer (which I'm not quite sure what it's worth, given that one of the items is a f sandvich) http://www.tf2outpost.com/trade/7068601 was offered 2 keys

http://www.tf2outpost.com/trade/7136341 was offered 2 keys

http://www.tf2outpost.com/trade/7251776 a quickbuyer, agreeing to go higher than a key.

http://www.tf2outpost.com/trade/7280779 offering a f grenade launcher, untaken

http://www.tf2outpost.com/trade/7101768 buying at 4 ref, no bites.

http://www.tf2outpost.com/trade/5439627 2 key buyer