How much is cab fare from Miami Airport to Port of Miami?

It cost us approximately $12.50 to GO to the cruise ship (including the additional $2.00 fee for trips originating at the airport); but it cost us $14.50 to return to the airport. We argued with the driver that the fee wasn't right, but he just gave us a hard time and said it's all up to the meter. The company was Yellow Cab.