If you go here
then click on the link for the prices, it will bring up a per item price list as a PDF. Again, I'm not sure if or when the ship will be offering the flat fee service.
2007 - Majesty of the Seas (Bahamas)
2009 - Enchantment of the Seas (Western Caribbean)
2010 - Freedom of the Seas (Western Caribbean)
2013 - Golden Princess (Alaska, roundtrip from Seattle)