Sale 1:

Sold for Terror Watt Brigade Helm (2.45*0.9) = 2.205 (rounding to 2.2)

http://backpack.tf/profiles/76561198100532201?time=1405456658 → http://backpack.tf/profiles/76561198055457557?time=1405407600

Sale 2:

Sold for Dead Presidents Whoopee Cap (2.97*0.9) = 2.673 (price is outdated, but B/O was 2, so pricing at 2)

http://www.tf2outpost.com/trade/21142473

http://backpack.tf/profiles/76561198055457557?time=1405345484 → http://backpack.tf/profiles/76561198045090105?time=1405321200

Sale 3: (credits to 'Pie Creepin 'Round Here' for proof)

Sold for Aces High Engineer's Cap (1.4*0.9) + *Steaming Barnstormer ([17.5/19]*0.9) = 1.26+ 0.83 = 2.09 (rounding to 2.1)

http://www.tf2outpost.com/trade/21256966

Sale 4:

Sold for 2 buds pure

http://www.tf2outpost.com/trade/21288688

Sale 5:

Sold for 46 keys pure ([46/19]) = 2.42 (rounding to 2.4)

http://www.tf2outpost.com/trade/21385249

Sale 6: (outlier)

Sold for Miami Nights Connoisseur's Cap (4.97*0.9) = 4.473 (invalid since price is outdated, but is evidently still an outlier)

http://www.tf2outpost.com/trade/21462703

http://backpack.tf/profiles/76561198056393192?time=1406925557 → http://backpack.tf/profiles/76561198101210576?time=1406876400

Sale 7: (invalid sale)

Cannot identify what it sold for

http://www.tf2outpost.com/trade/21692420

Sale 8: (invalid sale, Chieftains is outdated and need a price for the Unarmed Combat)

Sold for Blizzardy Storm Chieftains Challenge (1.6*0.9) + 4 keys (0.21) + Professional Unarmed Combat (?) = 1.44 + 0.21 + ? = 1.65 + ?

http://www.tf2outpost.com/trade/22202399

http://i.imgur.com/BpQcNv9.png

Notes:

One of the trades ( http://www.tf2outpost.com/trade/21692420 ), apparently got an offer of 2.3 pure: http://gyazo.com/bc63c7f6a48304ce1326d3a2b90b1dbc

*Steaming Barnstormer = http://backpack.tf/vote/id/5401e4694dd7b87a788b47ed

Feel free to support/counter my suggestion!