Cost was the 'decisive/deciding/determining factor' in their decision. [=the most important reason for their decision]
The 'deciding factor' was cost. [=the decision was based on cost; the least expensive option was chosen]
Costs increased/decreased by a 'factor' of 10. [=costs were 10 times higher/lower than they had been]
(..) of the bicycle. HODGINS: Well, yeah, I mean, -pound biker, a -pound bike, factor in the rate of acceleration and come on, I mean, it's your basic high school physics problem. Not in my high school. (..)2015 TvShow: Bones Title: The Promise in the Palace Season: 11 Episode 7