Sale 1:

Sold for 2 buds + 10 keys (0.54) = 2 + 0.54 = 2.54 (rounding to 2.5)

http://www.tf2outpost.com/trade/20539809

Sale 2:

Sold for Bubbling Charmer's Chapeau (1.4*0.9) + 1 buds + 3 keys (~0.16) = 1.26 + 1 + 0.16 = 2.42 (rounding to 2.4)

http://www.tf2outpost.com/trade/21141930 → http://i.imgur.com/zRYBvYI.jpg

Sale 3:

Sold for 36 keys pure (1.95) + Strange All-Father + Antarctic Parka ([5.75 + 1]*0.9) = 1.95 + 0.33 = 2.28 (rounding to 2.3)

http://www.tf2outpost.com/trade/21228974 → http://i.imgur.com/5kPPxsz.jpg

EDIT: Fixed links

Feel free to support/counter my suggestion!