That seems to be the cheapest I have found so we will probably go with it
You may also want to look into taking a taxi, depending on how many people in your party. I think it's about $75 each way, including tip, to taxi from Miami Airport to Port Everglades. If there are two of you, Royal Caribbean's transfers are a good deal. With more than two, it may pay to take a taxi.
On the way home, make sure your flight is later than 12:30pm. If the ship is delayed in getting cleared, you may be getting off the ship later than anticipated. Also, if you're among the first to get on the transfer bus, it won't leave until the bus is full, which could take 30+ minutes. It's true that if all works quickly, you could end up at the airport early, but it's better to take the stress out of that last morning and book an afternoon flight home.
I think RCI's transfers depend on the number of people as far as cost and comparison to taxis, etc. I think in Florida, going to and from Port Everglades from FLL, their costs were pretty competitive compared to a taxi if it was just one person.
Also, ask2112, if you have any carry on luggage you want to bring on the cruise, keep that with you on the bus, and not underneath the bus in the luggage compartment.
2007 - Majesty of the Seas
2009 - Enchantment of the Seas
2010 - Freedom of the Seas