The price needs an update. Easy to find it at 5.5 keys, a lot of unsolds at the current price. Proof is below.

Sellers:

http://www.tf2outpost.com/trade/8827995 - 6 keys, 1 week, unsold

http://www.tf2outpost.com/trade/8913161 - 6 keys, 5 days, unsold

http://www.tf2outpost.com/trade/8960358 - 6 keys, 3 days, unsold

http://www.tf2outpost.com/trade/8984301 - 6 keys, 2 days, unsold

http://www.tf2outpost.com/trade/9035837 - 6 keys, 2 days, unsold (he opens a new trade every day)

http://www.tf2outpost.com/trade/9020171 - 6 keys, 20 hours, no takers

http://www.tf2outpost.com/trade/9030228 - 6 keys, 14 hours, no takers

http://www.tf2outpost.com/trade/8850330 - 5 keys + 2 ref, unsold, 1 week

http://www.tf2outpost.com/trade/9031283 - 5 keys + 2 ref, 13 hours, no takers

http://www.tf2outpost.com/trade/9032497 - 5 keys + 2 ref, 12 hours, no takers

http://www.tf2outpost.com/trade/8796769 - 5 keys + 1 ref, willing buyer (retracted)

http://www.tf2outpost.com/trade/8936671 - sold for 5 keys

Buyers:

http://www.tf2outpost.com/trade/9008712 - 5 keys, bought

http://www.tf2outpost.com/trade/8955538 - 5 keys, 3 days, no takers

http://www.tf2outpost.com/trade/9029507 - 5 keys, no takers

http://www.tf2outpost.com/trade/8678409 - 4 keys + 3 ref, 1 week, no takers

http://www.tf2outpost.com/trade/8742607 - 4 keys + 2 ref, 1 week, no takers

http://www.tf2outpost.com/trade/9030926 - 4.5 keys, no takers

http://www.tf2outpost.com/trade/9024762 - Genuine Brigade Helm (5 keys in items), no takers

http://www.tf2outpost.com/trade/9021400 - 4 keys, no takers

Also in the Steam Market average price is about 14$ (12.1$ without fees). Keys average price is 2.20$, so a seller would receive ~5.45 keys

http://steamcommunity.com/market/listings/440/Strange%20Gold%20Botkiller%20Scattergun%20Mk.II

http://steamcommunity.com/market/listings/440/Mann%20Co.%20Supply%20Crate%20Key