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]
(..) we sway public opinion. The battles lost. Now to that effect. My team have come up with a pretty aggressive new campaign. Wow factor off the charts. We need to give the Americans a product they can love. A figure they can rally behind. Sir, I have dissected this bill. (..)2014 RoboCop