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]
(..) until tomorrow. Selection before the following emotional responses. You have . seconds to enter your emotional response. Reaction time is a factor. Please make a selection for the following emotional responses. You have . seconds to enter your emotional response. Does this thing end? (..)1997 The Game