http://www.tf2outpost.com/trade/6586249 Sold for a kringle (Just put this here for fun)

http://www.tf2outpost.com/trade/5355368 Sold for 2 keys + 3 ref (3 weeks ago, but the last suggestion was 2 months ago)

http://www.tf2outpost.com/trade/6501147 Sold for 2 keys (You can tell he's underpricing ALL of those)

http://www.tf2outpost.com/trade/6591643 Offer of 2 keys 1 ref (Wanted higher backpack.tf price though)

http://www.tf2outpost.com/trade/6367555 Sold for 8 ref

http://www.tf2outpost.com/trade/6616815 Offer of a low-ish craft Area 451

http://www.tf2outpost.com/trade/5001420 Unsold for 3 keys for 1 month, offer of 1 key + 4 ref (A little old, but still...)

http://www.tf2outpost.com/trade/6173387 Bought for 3 keys (had a worthless paint on it)

http://www.tf2outpost.com/trade/4771182 Unsold for 8 ref, 1 month old offer of Aspect, G. AWP, Hoodie, and 2 scrap

http://www.tf2outpost.com/trade/6305508 Sold for 6 ref and a nice story

http://www.tf2outpost.com/trade/6332961 Someone willing to buy it for 3 keys, doesn't look like it went through yet

http://www.tf2outpost.com/trade/6326791 1 key + 4.66 offer, declined

http://www.tf2outpost.com/trade/6636780 Sold for 7 ref

My point is, its somewhat hard to sell for 3 keys, but people are still willing to do it. Most other offers are in the suggested range.