Sellers

http://www.tf2outpost.com/trade/8016541 1day old, asking for 3keys of items, no takers, offer of 2keys(you will see this buyer on every seller link, he not been successful and will not be mentioned in the links again)

http://www.tf2outpost.com/trade/8030365 1day old, offer of 3keys(got one elsewhere to resell)

http://www.tf2outpost.com/trade/8047305 1day ago, asking 3keys

http://www.tf2outpost.com/trade/8020498 1day ago, asking 2keys+3ref

http://www.tf2outpost.com/trade/7065585 1month old, offer of a clean headtaker 1week ago

http://www.tf2outpost.com/trade/7762424 1week old, offer of 9ref, willing to accept 2keys+3ref

Buyers

http://www.tf2outpost.com/trade/7915173 reverse bid, offer of 2keys+3ref(from one of the seller links)

Conclusion: Buyers have very little interest in these, the 2key buyer was pretty much the only offer all of these received in the last week. Sales at 3keys rarely happen. I chose 2.75-3keys because there is no interest in the 3key sellers, but prices below 2.9 keys have not been proven yet.