Updating the price. Proof is below. Nobody is willing to sell at 5 keys anymore. Still possible to buy it for 6 keys, but some buyers are willing to pay more.

Sellers:

http://www.tf2outpost.com/trade/9239895 - 8 keys, 1 week, unsold, got offered 7 keys (retracted)

http://www.tf2outpost.com/trade/9265320 - 7.25 keys, 1 week, no takers

http://www.tf2outpost.com/trade/9061310 - 7 keys, 1 week, got offered 6 keys (3 times)

http://www.tf2outpost.com/trade/9364366 - 7 keys, 4 days, unsold, but had a willing buyer for 7 keys (he bought it from someone else)

http://www.tf2outpost.com/trade/9422694 - 7 keys, 2 days, unsold

http://www.tf2outpost.com/trade/9230022 - unrealistic B/O, got offered 6 keys

http://www.tf2outpost.com/trade/9473081 - 7 keys, still new trade

http://www.tf2outpost.com/trade/9472367 - 6 keys, still new trade

http://www.tf2outpost.com/trade/9443475 - 6 keys, 1 day, unsold (without bumps)

http://www.tf2outpost.com/trade/9410642 - sold 2 at 6.5 keys each. This is my trade. Initially I tried to sell it at 7 keys, but unsuccessfully, then lowered the price to 6.5 keys and sold both in less than a day. Proof of sale: http://i.imgur.com/SFXl2tb.png http://i.imgur.com/mN0Zx31.png

To prevent your questions - the first one I bought for 6 keys ( http://www.tf2outpost.com/trade/9269606 ), the second one I bought from the steam market very cheap (something like 7 USD)

http://www.tf2outpost.com/trade/9231973 - sold for 7 keys

http://www.tf2outpost.com/trade/9241090 - sold for 7 keys (with dominations kills attached, basically ~ 6.25 - 6.4 keys without the strange part)

http://www.tf2outpost.com/trade/9241524 - sold for 6 keys (at once 2 willing buyers)

http://www.tf2outpost.com/trade/9253420 - sold for 6 keys

Buyers:

http://www.tf2outpost.com/trade/9274230 - bought for 6 keys

TF2Warehouse is buying it at 73,690 credits (~5.6 keys), 0 in stock (nobody is willing to sell at this price).

http://www.tf2wh.com/pricelist.php

http://www.tf2wh.com/items.php?search=blood