So after this disaster with the currency here we go once more: (shoutout to Duscoda for telling me)

Bump on that 4 months old price, themed hat, unfortunally impossible to find without white paint :D.

http://www.tf2outpost.com/trade/6648649 2 buds, 13 keys salvage 40 offer ~ 2.6

http://www.tf2outpost.com/trade/11408192 roboactive gridiron (3.9buds Oo), though it is not stated in the comments, second best is clean black max (2.2)

http://www.tf2outpost.com/trade/10038365 50 keys pure + 10 keys in sweets (2.5)

http://www.tf2outpost.com/trade/11373433 black clean max (2.2)

http://www.tf2outpost.com/trade/11491750 ts max lvl64 (2.2)

http://www.tf2outpost.com/trade/11717912 sold for ~55 keys ~2.3 bud

I'll constantly look for more proof, personal experience is always welcomed :).