Let's try this again- left out the range last time.

Sale 1

[No OP-Trade] Sold for Nuts Fed-Fightin'

X = 14*0.9

X = 13 keys

Fed-Fightin' http://backpack.tf/item/2526215488

Capo http://backpack.tf/item/1152995060

Sale 2

http://www.tf2outpost.com/trade/24168697 Sold for Stormy Berliner's

X = 15*0.9

X = 14

Berliner's http://backpack.tf/item/1335408467

Capo http://backpack.tf/item/1152995060

Mini for Berliner's

2 Common B/Os of 15 keys on Classifieds, using 15 keys

Sale 3 OUTLIER

http://www.tf2outpost.com/trade/24132686 Sold for Aces Necessities

X = 0.9*0.9

X = 0.8

X = 10 keys at the time

Bear http://backpack.tf/item/2210021475

Capo http://backpack.tf/item/1152995060

Many thanks to Sugarcube for the evidence!