While making this, the other suggestion was accepted (I have no clue about non-currency item cooldowns)

Sold over 2 ref:

http://www.tf2outpost.com/trade/23845561 3 ref

Sold for 4 ref:

http://www.tf2outpost.com/trade/23790813

http://www.tf2outpost.com/trade/23773932

http://www.tf2outpost.com/trade/23832835

http://www.tf2outpost.com/trade/23874709 (not in his/her bp)

Sold over 4 ref:

http://www.tf2outpost.com/trade/23787416 4,66 ref, (not in his/her bp)

http://www.tf2outpost.com/trade/23809627 6 ref

http://www.tf2outpost.com/trade/23794229 1 key (not in his/her bp)

http://www.tf2outpost.com/trade/23749104 1 key (not in his/her bp)

Current sellers on outpost:

http://www.tf2outpost.com/trade/23895093 1.66 ref (young)

http://www.tf2outpost.com/trade/23900977 2.33 ref (young)

http://www.tf2outpost.com/trade/23866337 4 ref

http://www.tf2outpost.com/trade/23773932 4 ref (has sold some)

http://www.tf2outpost.com/trade/23836962 5 ref

http://www.tf2outpost.com/trade/23818480 5 ref

http://www.tf2outpost.com/trade/23814702 5 ref

http://www.tf2outpost.com/trade/23898641 6 ref

http://www.tf2outpost.com/trade/23900584 10 ref

http://www.tf2outpost.com/trade/23723519 1 key

http://www.tf2outpost.com/trade/23780122 1 key

http://www.tf2outpost.com/trade/23745494 1 key

http://www.tf2outpost.com/trade/23825890 1 key

http://www.tf2outpost.com/trade/23702971 1 key

http://www.tf2outpost.com/trade/23743582 1 key

http://www.tf2outpost.com/trade/23898698 1 key

http://www.tf2outpost.com/trade/23722857 1 key

So, all current sellers below 4 ref are young and 4 ref seems to be the most common trading point and all sales over that seem to be pretty rare, so 4 ref for the price

All counter/supportive proof is welcomed

Please don't steal my proof