Well then, didn't expect this one!

Thanks to Cashew for confirming his sale as an outlier.

Sale 1) Sold for 18 keys pure

http://backpack.tf/profiles/76561198107791241?time=1442386800&compare=1442300400

https://gyazo.com/d7352ba78bc4876f416aa1a44f443cb1 Screenshot of above

Sale 2) Paid 15 keys for HW and a NNB Hetmans (outlier)

http://backpack.tf/profiles/76561198067575136?time=1438239600&compare=1438326000

https://gyazo.com/5c4fca2939090b8285b9f78bed97f364

Sale 3) Sold for 18 pure (checked history by history)

http://backpack.tf/profiles/76561198004236703?time=1437807600&compare=1437894000

https://gyazo.com/68e9e3a4e76a39e473ff78d9e30b7448 Screenshot of above

Sale 4) Sold 1:1 for a Bubbling CM

http://backpack.tf/profiles/76561198003161689?time=1437375600&compare=1437289200

https://gyazo.com/25c164d095094a0f7ac16b14ce7993fb Screenshot of above

X = 21*0.9

X = 19

Sales at: 18, 18 and 19

Any advice about this one would be nice.

Beep Boop, end of suggestion.