We are booked on a 5 night carribean cruise on the magic in January. I looked at a 7 night in January and for the same type of room, inside statroom it was almost $3000 more in total. Both carribean cruises, both in January, both for inside staterooms.
It still depends on the dates - are you in early January over New Years or later the first week where schools are still out? Is it over MLK day when you might find people willing to add that day into a vacation? These two sailings will be much more expensive. Are the itineraries the same? The 5 night likely only goes to Cozumel, where the 7 night WC goes to Cozumel, Grand Caymen, and Falmouth. Or is it an EC itinerary on the Fantasy, which goes to Tortola and St. John/St. Thomas? Prices differ primarily on time of year and itinerary, with the Dream class ships being slightly more expensive for the Carribbean sailings.
Does the 7 night cruise have different/more port stops? Each port has it's own fees and taxes that must be paid. More ports = more cost. Even just 2 more sea days = more food/entertainment necessary onboard.
As noted, it's a combination of both.
The bigger ships are newer and have more bells & whistles: Aqua Duck, Remy, Midship Detective Agency, virtual sports, mini-golf, magical portholes in inside staterooms, Disney movies on-demand in staterooms, etc. Disney does charge a premium for all that.
