DISCLAIMER: I have 6 of these

There was a general consensus that the lower end needed to be 3 keys, which is what I've done. Seeing sales/offers at 4 keys though (and I've sold a few at this price)

SOLD/WILLING BUYERS:

http://www.tf2outpost.com/trade/3049234 1.5 keys (Sold)

http://www.tf2outpost.com/trade/4914363 2 keys + 0.66 ref (so many willing buyers, poster unresponsive for months)

http://www.tf2outpost.com/trade/5084191 3 keys (lots of willing buyers)

http://www.tf2outpost.com/trade/7899946 3 keys (lots of willing buyers)

http://www.tf2outpost.com/trade/7911326 3 keys (SOLD)

http://www.tf2outpost.com/trade/5754150 3 keys (SOLD)

http://www.tf2outpost.com/trade/6090994 3 keys (SOLD)

http://www.tf2outpost.com/trade/7981380 3 keys (SOLD)

http://www.tf2outpost.com/trade/7059843 3 keys (SOLD)

http://www.tf2outpost.com/trade/7894850 3 keys (SOLD)

http://www.tf2outpost.com/trade/7640812 3 keys (All sold)

http://www.tf2outpost.com/trade/6432022 3 keys (All sold)

http://www.tf2outpost.com/trade/7997590 3 keys (All sold)

http://www.tf2outpost.com/trade/8053715 3 keys (All sold)

http://www.tf2outpost.com/trade/5160137 3 keys + 1 ref (0 in stock)

http://www.tf2outpost.com/trade/7915559 3.5 keys (Sold)

http://www.tf2outpost.com/trade/8006789 3.5 keys (Sold)

http://www.tf2outpost.com/trade/4777064 4 keys (1 in stock, 13 sold (at least some at 3 keys))

STILL NEW:

http://www.tf2outpost.com/trade/8087727 (3 keys)

UNSOLD:

http://www.tf2outpost.com/trade/8057834 4 keys

http://www.tf2outpost.com/trade/8043005 4 keys

http://www.tf2outpost.com/trade/8082876 4 keys (sold one + 6 keys for Black Bills)

http://www.tf2outpost.com/trade/7946430 4 keys (3 key offer ignored)

http://www.tf2outpost.com/trade/7784889 4 keys (3 key offer ignored)

http://www.tf2outpost.com/trade/8055741 4 keys (3 key offer declined)

http://www.tf2outpost.com/trade/7816097 4 keys (3 keys declined, 3 + clean fez hidden)

http://www.tf2outpost.com/trade/5113872 5 keys

http://www.tf2outpost.com/trade/5683509 5 keys (My trade)

QUICKBUYERS

http://www.tf2outpost.com/trade/7731488 3 keys (a few adds in the last week)

http://www.tf2outpost.com/trade/8090785 3 keys (no offers yet)

http://www.tf2outpost.com/trade/7999492 3 keys (1 add 2 days ago, but still has keys)

OTHER SOURCES

Steam market average (24 hours): 7.71 USD (8 sold) ~5.61 keys (According to this site)

TF2TP - loads sold at 3 keys

http://tf2tp.com/trade.php?trade=9037640 3 keys (Unsold but fairly new)

http://tf2tp.com/trade.php?trade=9040638 3 keys (Unsold but fairly new)

http://tf2tp.com/trade.php?trade=9030188 3.5 keys (Sold)

http://tf2tp.com/trade.php?trade=9022797 3.5 keys (Sold)

http://tf2tp.com/trade.php?trade=9018553 3 keys + 2 ref (Sold)

TF2WH

34,380c (approx 3.25 keys) - 0 in stock

BACKPACK.TF - 0 in classifieds