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]
(..) that landed that plane on the river as much as the mechanics of the aircraft. Are you saying that Captain Sully wasn't a hero? No, no. There were just other factors. Are you not an American? Hey, fuckface, you want to get your shit out of my car or what? I... Yeah. (..)2011 Friends with Benefits