Sale 1: (credits to aaroncsn for the fix-up!)

Sold for Hearts Hound Dog (3.1*0.9) + 15 keys (~0.79) = 2.79 + 0.79 = 3.58 (rounding to 3.6)

http://www.tf2outpost.com/trade/20825357

http://backpack.tf/profiles/76561198081944217?time=1404111600

Sale 2: (Quicksale)

Sold for 2 buds within a day

http://www.tf2outpost.com/trade/20824963

Sale 3:

Sold for DBD Noble Amassment (4.5*0.9) = 4.05 (rounding to 4)

http://www.tf2outpost.com/trade/21983190

http://backpack.tf/profiles/76561198024654687?time=1408086000 → http://backpack.tf/profiles/76561198087223342?time=1408086000

Sale 4:

Unsure what it sold for, backpack histories aren't helping either. Thus, invalid sale.

http://www.tf2outpost.com/trade/21220863

Notes to support range:

http://www.tf2outpost.com/trade/20870032 - offer of Logo Tossle (3.3*0.9) + 16 keys (~0.84) = 2.97 + 0.84 = 3.81

Feel free to support/counter my suggestion!