Sale 1:

Sold for Nuts n' Bolts Billycock (0.68*0.9) + Australium Knife (1.4*0.9) = 1.88 (rounding to 1.9)

http://www.tf2outpost.com/trade/21946191

http://backpack.tf/profiles/76561198132527164?time=1407913200 → http://backpack.tf/profiles/76561198132527164?time=1407999600

Sale 2:

Sold for DBD Billycock (2.3*0.9) = 2.07 (rounding to 2.1)

http://www.tf2outpost.com/trade/22008770

http://backpack.tf/profiles/76561198050434553?time=1408258800 → http://backpack.tf/profiles/76561198132527164?time=1408172400

Sale 3:

Sold for Australium Knife (1.4*0.9) + Big Kill (0.63*0.9) = 1.26 + 0.57 = 1.83 (rounding to 1.8)

http://www.tf2outpost.com/trade/21936875

http://backpack.tf/profiles/76561198082314239?time=1407740400 → http://backpack.tf/profiles/76561198082314239?time=1407913200

Sale 4: (obvious outlier)

Sold for Miami Nights Cold Killer (3.9*0.9) = 3.51 (rounding to 3.5)

(no outpost trade since one of them is banned on there)

http://backpack.tf/profiles/76561198071381455?time=1407913200 → http://backpack.tf/profiles/76561198037738696?time=1407913200

Feel free to support/counter my suggestion!