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]
(..) Come on, you know better than anyone... ...the weight on any pendulum has no effect on speed. It doesn't affect frequency, but it's totally a factor in momentum. Hey, Aunt May. Yeah.Eggs? Organic, got it. In the future, if you're gonna steal cars... (..)2012 The Amazing Spider-Man