There is one factor that hasn't been mentioned here, which is mentioned in the document: they can accomodate 1200 magicians if every room is shared. But most people will not want to share a tiny stateroom, which means the number of attendees would probably be 700. That greatly limits FFAP's income, and I would imagine that this is one of the big reasons why they've scuppered the idea of the cruise ship.
(Incidentally, there have been many "Magic Cruises"--conventions on cruise ships--which have originated in the United States.)
Is it a coincidence that this announcement has come only a week after the catastrophe on Carnival Cruise lines in which their ship was stranded with no electricity or working toilets and the people were walking in feces-contaminated water and sleeping in mattresses on the deck of the boat? Every one of the passengers on that boat is going to sue Carnival Cruise Line, and perhaps FFAP thought that if such an event happened to them, it would bankrupt and destroy their organization.
Personally, I am glad that the convention won't be on a cruise ship--I didn't want to pay a lot of money to stay in a tiny cabin! I am much more likely to go to the convention if it's in a major city in France. Perhaps others feel that way, too. I really don't know what the average attendance of an FFAP convention is. But this is the first time it will host FISM Europe, so the number of attendees would likely be higher.
Craig, after the terrible job that Derek Lever did in putting on FISM, I would imagine that it would be unlikely he would be given the FISM Europe competition again.