Flat or per seat: the model matters more than the number
Flat-fee CRM licensing is an appealing answer to seat counting, and for the right team it is genuinely cheaper. For the wrong team it is capacity you pay for and do not use. The only way to know which you are is to divide, honestly, by the number of people who will really open the CRM every week.
Cost per active user is the comparable figure
A flat organisation fee divided by active users gives a number you can hold next to a per-seat rate. Do the division twice: once for the team you have and once for the team you expect in eighteen months. Small or stable teams usually land better on per-seat pricing with no minimum. Large or fast-growing teams often cross over.