Proof:

Last Suggestion Proof (Credits to [EFR] TheKaushuMan™):

Sales at 1 key/7 ref:

http://www.tf2outpost.com/trade/16410578 multiple adds

http://www.tf2outpost.com/trade/16879303

http://www.tf2outpost.com/trade/17055716

http://www.tf2outpost.com/trade/17047750

http://www.tf2outpost.com/trade/17033915

http://www.tf2outpost.com/trade/17008312

http://www.tf2outpost.com/trade/12407580 multiple recent adds

http://www.tf2outpost.com/trade/17075529 buyer at a key

http://www.tf2outpost.com/trade/17038897 buyer at a key

My Proof:

http://www.tf2outpost.com/trade/17149896 - Sold for 6 ref without a bump (quicksell)

Sales at 1 key/7 ref:

http://imgur.com/2LTxFkn

http://www.tf2outpost.com/trade/16410578

http://www.tf2outpost.com/trade/17113737 - Less than a day

http://www.tf2outpost.com/trade/17134797 - Less than a day

http://www.tf2outpost.com/trade/17134497 - 13 hours

http://www.tf2outpost.com/trade/17146385 - 8 hours

http://www.tf2outpost.com/trade/17109844 - 5 hours

http://www.tf2outpost.com/trade/17156143 - 3 hours

http://www.tf2outpost.com/trade/17133471 - 1 hour

http://www.tf2outpost.com/trade/17138504 - Without a bump

I only showed 1 quicksale at below 1 key but with so many recent (even the last suggestion can be considered recent, it was opened 3 days ago...) 6 really seems like an outlier

The only reason 6 was in range is because it was a conservative bump

I can find more quicksales to show that anything below 7 is a quicksell but I think that with this amount of sales at 1 key and this time they took, without a bump - less than a day, which is pretty fast, is enough to show even a key sells fast

Also keep in mind there are 5 pages on outpost when around half are in sets/parts/killstreaks (it's without australium though)