Airport to Port by grandmaR
The cheapest way to get from the airport to the port is to come in a day in advance and rent a car from Dollar. They have a free shuttle to the rental place which is not on the airport property. Then the next day, turn the car in, and they have a free shuttle to the port. Of course you would have to pay for the hotel and car and meals, but the getting to the port is free.
Otherwise, I'm afraid it is a taxi or a transfer arranged by the cruise ship.