Sale 1:

Sold for 1 buds + 39 keys = 1 + 2.1 = 3.1

http://www.tf2outpost.com/trade/21674383 ? http://backpack.tf/profiles/76561198043769344?time=1406876400

Sale 2:

Sold for Clean Max's Severed Head = 3.05 (rounding to 3.1)

http://www.tf2outpost.com/trade/21205604

Sale 3:

Sold for 3.5 buds pure = 3.5

http://www.tf2outpost.com/trade/20307473

Sale 4: (happened a bit over 2 months ago, but still shows that sales were close back then)

Sold for Logo YWN + 1 buds = (2.3*0.9 = 2.07) + 1 = 3.07 (rounding to 3.1)

http://www.tf2outpost.com/trade/19191991

Notes:

http://www.tf2outpost.com/trade/19191991 - been offered a Max's Head (~3.1)

Feel free to support/counter my suggestion!