First price suggestion, let's go mates. I can handle constructive criticism, so if you can suggest a better range, go for it.

Bringing it back down a little bit. 1.5 keys is 1 key, 4 ref. This seems to be very possible, but not the norm.

Unsold:

http://backpack.tf/classifieds/search/id/52c9131f4dd7b8c4618b456a 1 key, 4 ref (At the time of my posting backpack classifieds has 3 unsold, two over a day old and the newest one at 22 hours.)

http://www.tf2outpost.com/trade/19015619 1 key, 4 ref (1 day old)

http://www.tf2outpost.com/trade/19038654 1 key, 5 ref (Only 6 hours old at the moment)

http://www.tf2outpost.com/trade/19026557 1 key, 5 ref (17 hours old)

http://www.tf2outpost.com/trade/19002290 1 key, 6 ref (1 day old)

http://www.tf2outpost.com/trade/19002283 1 key, 6 ref (1 day old)

http://backpack.tf/u/76561198068917275 1 key, 6 ref (3 hours old, might have been relisted (I don't know if it's possible to tell))

http://www.tf2outpost.com/trade/18950841 1 key, 6.66 ref (3 days old)

http://www.tf2outpost.com/trade/18965654 1 key, 7 ref (3 days old)

http://www.tf2outpost.com/trade/19016018 1 key, 7 ref (1 day old)

http://www.tf2outpost.com/trade/19040035 1 key, 7 ref (Only 2 hours old. Should I bother including stuff like this?)

http://www.tf2outpost.com/trade/18960261 2 keys (3 days old)

http://www.tf2outpost.com/trade/18890188 2 keys (1 week old)

http://www.tf2outpost.com/trade/18994478 2 keys (1 day old)

http://www.tf2outpost.com/trade/18990285 2 keys (2 days old)

http://www.tf2outpost.com/trade/18975206 2 keys (2 days old)

http://www.tf2outpost.com/trade/18867203 2 keys (1 week old)

http://www.tf2outpost.com/trade/18643321 2 keys (2 weeks old)

http://www.tf2outpost.com/trade/18977451 2 keys (4 total, all unsold after 2 days)

http://www.tf2outpost.com/trade/18978384 2 keys (8 total(?) none sold after 2 days)

http://www.tf2outpost.com/trade/18743565 2 keys (2 weeks old)

http://www.tf2outpost.com/trade/18966556 2 keys (3 days old)

http://www.tf2outpost.com/trade/18968186 2 keys (3 days old)

http://www.tf2outpost.com/trade/18935628 2 keys (4 days old)

http://www.tf2outpost.com/trade/18923200 2 keys (5 days old)

http://www.tf2outpost.com/trade/18981134 2 keys (2 days old)

Apparently 2 keys is not impossible though. Recent solds include:

http://www.trade.tf/trade/532255800 1 key, 4.27 ref (Probably sold for 4.33)

http://www.tf2outpost.com/trade/19009267 12 ref

http://www.tf2outpost.com/trade/19029518 2 keys

http://www.tf2outpost.com/trade/19026869 2 keys

http://www.tf2outpost.com/trade/19000869 2 keys

Well there we go. Let me know if I need more proof, or better proof, or a better range, or if I should just kill myself. Cheers.