8 months since i owned mine :/

http://www.tf2outpost.com/trade/16419155 sold for b/o buds were 17 keys = 4

http://www.tf2outpost.com/trade/15589538 sold for stormy headwarmer(1.65) + 49(3.05) keys = 4.7

http://www.tf2outpost.com/trade/14588789 sold for ks headwarmer, had b/o at 4.6

literally the only proof i could find

while yes on link 1 it may seem like he paid 72 keys, the b/o was 68 and the 4 keys were just added for holding, and not really part of the actual sale imo. the b/o is 68 keys, and the sale value cant be over its b/o

doing 4-4.7, the ks headwarmer sale shouldn't be valued over its b/o, so it'll just be in range