Sale 1:

Sold for 5 buds pure

http://www.tf2outpost.com/trade/20929769

http://backpack.tf/profiles/76561198062483845?time=1408863600

Sale 2: (complex sale)

Sold with Scorching Private Eye + Burning Noble for GE Executioner + TS Bills + 9 keys

http://www.tf2outpost.com/trade/20901681

http://backpack.tf/profiles/76561198069980430?time=1404521963 → http://backpack.tf/profiles/76561198004132815?time=1404457200

Sale 3:

Sold for Cloudy Moon Fruit Shoot (4.8) = 4.8 (no overpay, offer)

http://www.tf2outpost.com/trade/20967471 → http://www.tf2outpost.com/trade/21030410

http://backpack.tf/profiles/76561198069980430?time=1404716400 → http://backpack.tf/profiles/76561198036684395?time=1404774092

Sale 4: (invalid sale, oudated price)

Sold for Cloud 9 Tyrant's Helm (5.15*0.9) = 4.635

http://www.tf2outpost.com/trade/21048071

http://backpack.tf/profiles/76561198015491724?time=1405213597 → http://backpack.tf/profiles/76561198036684395?time=1405148400

Sale 5: (outlier)

Sold for Haunted Ghosts Slick Cut (3.5*0.9) = 3.15

http://www.tf2outpost.com/trade/21169368

http://backpack.tf/profiles/76561198078227700?time=1405259343 → http://backpack.tf/profiles/76561198015491724?time=1405321200

Sale 6:

Sold for Phosphorous Ze Goggles (2.1*0.9) + Australium Medi Gun (1.65*0.9) + 2 buds (2) = 1.89 + 1.485 + 2 = 5.375 (rounding to 5.4)

http://www.tf2outpost.com/trade/21195283

Sale 7: (invalid sale)

Unsure what it sold for

http://www.tf2outpost.com/trade/21374076

Sale 8: (invalid sale, outdated price)

Sold for Orbiting Fire Crone's Dome (6.15*0.9) = 5.535

http://www.tf2outpost.com/trade/22078928

http://backpack.tf/profiles/76561197999139658?time=1408475344 → http://backpack.tf/profiles/76561198004175105?time=1408431600

Sale 9: (outlier)

Sold for Level 1 Max's Head (3.3*0.9) + Stormy Storm Mirror (1.25*0.9) + 5 keys (~0.26) = 2.97 + 1.125 + 0.26 = 4.355 (B/O was 4, valuing at 4)

http://www.tf2outpost.com/trade/22096741

http://backpack.tf/profiles/76561197999139658?time=1408518000 → http://backpack.tf/profiles/76561198104366533?time=1408863600

Feel free to support/counter my suggestion!