Florence is served by the ports of Livorno and La Spezia, but isn't itself a cruise port. Together, Livorno and La Spezia is the embarkation point for only thirty cruises every year from MSC to the Mediterranean.
Overall sailings from Florence are rather affordable compared to other ports. Cruises leaving from Florence during the the peak season of summer are significantly more expensive than the the low season of fall. The illustration below shows the monthly average cost per day for cruises from Florence (Cruises only depart from Florence between April and November).