Updating the price. Proof is below. Easy to sell at 4 keys, a bit difficult at 4.5 keys and nobody wants to buy for 5 when there are a lot of cheaper ones in the market.

Sold:

http://www.tf2outpost.com/trade/10317124 - sold for 3.5 keys

http://www.tf2outpost.com/trade/10370804 - sold for 4 keys

http://www.tf2outpost.com/trade/10483789 - sold for 4 keys

http://www.tf2outpost.com/trade/10464371 - sold for 4 keys

http://www.tf2outpost.com/trade/10382930 - sold for 4 keys

http://www.tf2outpost.com/trade/10306091 - sold for 4.5 keys

Unsold:

http://i.imgur.com/7c4mseB.png - 4 keys 9 hours; 4.5 keys 2 days; 4.5 keys 5 days; 5 keys 4 days

http://www.tf2outpost.com/trade/10514617 - 4 keys, still new trade

http://www.tf2outpost.com/trade/10471110 - 4 keys, 2 days (without bumps)

http://www.tf2outpost.com/trade/10412380 - 4.1 keys, 2 days (with a medics killed attached)

http://www.tf2outpost.com/trade/10429042 - 4.4 keys, 2 days

http://www.tf2outpost.com/trade/10467449 - 4.5 keys, 2 days

http://www.tf2outpost.com/trade/10483717 - 4.6 keys, 1 day

http://www.tf2outpost.com/trade/10468453 - 4.6 keys, 2 days

http://www.tf2outpost.com/trade/10223669 - 5 keys, 1 week

http://www.tf2outpost.com/trade/10325714 - 5 keys, 1 week

http://www.tf2outpost.com/trade/10458510 - 5 keys, 3 days

http://www.tf2outpost.com/trade/10460204 - 5 keys, 3 days

Steam Market average price is 4.75 keys (less than the current high-end): http://i.imgur.com/Yn9dDe6.png