Ok let's try it again. Hope i did better this time :3 (still my second suggestion) I really thank you if you can find more proof!

Edit: yolo removed.

9 months old price.

http://backpack.tf/classifieds/search/vintage%20backbiter one for 5 ref, few non-painted ones for 1 key

UNSOLDS (1 KEY):

http://www.tf2outpost.com/trade/12200535 gold painted, 1 day (pretty new)

http://www.tf2outpost.com/trade/11719372 2 weeks

http://www.tf2outpost.com/trade/12145576 3 days

http://www.tf2outpost.com/trade/11429992 3 weeks

http://www.tf2outpost.com/trade/11139446 1 month

http://www.tf2outpost.com/trade/12139927 3 days

http://www.tf2outpost.com/trade/11998292 1 week

http://www.tf2outpost.com/trade/11889943 1 week

http://www.tf2outpost.com/trade/12117985 3 days

http://www.tf2outpost.com/trade/12066743 5 days

http://www.tf2outpost.com/trade/12160354 2 days

http://www.tf2outpost.com/trade/11569180 painted, 3 weeks

http://www.tf2outpost.com/trade/12222047 pretty new, 18 hours

http://www.tf2outpost.com/trade/11884763 1 week

SELLERS LESS THAN 1 KEY:

http://www.tf2outpost.com/trade/12140412 asks one key, but gives 0.33 back

http://www.tf2outpost.com/trade/12149818 asks 1 key, gives 0.66 back (same guy as in the classfields by the way)

http://www.tf2outpost.com/trade/12209358 4.66 (quicksell?)

http://www.tf2outpost.com/trade/11990401 5.33(1 key) But key is rising on price, so...

http://www.tf2outpost.com/trade/12184467 5 ref

OFFERS LIKE 1 KEY OR SOMETHING LIKE THAT:

http://www.tf2outpost.com/trade/11978228 clean ninepipe-problem(2.66) + 3 ref= 5.66 (looks like bought one)

SUCCESFULL BUYER: http://www.tf2outpost.com/trade/11416913 clean backbiter(1.33) + 3.66= 5 ref (3 weeks, don't know is it old trade for you guys lol)

Less than one page buyers. Most are quicksell-buyers.

http://www.tf2outpost.com/trade/10233919 collecting, willing to pay one key each(In metal 5.11),

has bought many

Note in his trade: *All prices change when the price of Billycocks change

SOME TF2TP SELLERS:

http://tf2tp.com/trade.php?trade=9565344 5 ref

http://tf2tp.com/trade.php?trade=9560321 5 ref(painted)