Cruise ships do not have sketchy registry, all Royal Caribbean fleet are registered in the Bahamas, Holland America is registered in Holland, Carnival is registered in Panama and Bahamas , Celebrity are registered in Malta.
There are no cruise ships , zero, registered in Liberia.
used cruise ships and second tier boats get sold into the euro and asian markets doing mediterrainian runs and south china/indo china runs where the market is 12 months of the year. They dont move the fleet like big players. The boats are cents on the dollar when a big name is done, however the operating costs are almost the same. You can find lots of Italian/Greek trips on Iberian cruiselines for much less than say Royal Norwegian, but it will be an old boat (if that matters) .
Mortgages on these boats are held by a variety of investment companies, Carnival (who own a half dozen lines) self finance some through holding companies, insurance companies have money in these things. Its a really big business, and since the crews are pulled from ALL over the planet, its not just a FLA company that implodes, it starves a town in the Philippines , the on board shops are run by south africans, musicians are from eastern europe, cooks from all over europe. This truely is a global business.
But i'm still not going for a year.....