Jacob allowed me to fix his suggestion :P

Sale #1:

Sold for a Kill-a-Watt Armored Authority:

http://www.tf2outpost.com/trade/26856590

Seller's backpack before: http://backpack.tf/profiles/76561198110986871?time=1441522800

Seller's backpack after: http://backpack.tf/profiles/76561198110986871?time=1442214000

Total: 19*0.9 = 17.1 keys

Rounding it down to 17 keys

Mini Suggestion for the Kill-a-Watt Armored Authority:

http://backpack.tf/vote/id/560daf17dea9e990334ac03a (Credits to Foamy the Fearsome)

Sale #2:

Sold for a Steaming Noble Assessment of Hats:

http://www.tf2outpost.com/trade/26882402

Seller's backpack before: http://backpack.tf/profiles/76561198066207210?time=1440572400

Seller's backpack after: http://backpack.tf/profiles/76561198066207210?time=1440658800

Total: 17*0.9 = 15.3 keys

Rounding it down to 15 keys

The outlier sales: http://backpack.tf/vote/id/560bac00dea9e9712a19625b

Please tell me if I made a mistake.