Live on board, how does that work and how much does it cost?
I imagine those who do this have their agent arrange it through the cruise line and they negotiate a special rate. I wouldn't be surprised if some form of financial guarantee had to be established.
Costs in the U.S. for a senior citizen assisted living facility can easily top $100,000 per year for a married couple. In fact that is probably below the median. It depends on the location. So, if you are looking at paying $280 per day I guess it is easy to see how a ship can be cheaper and offer more than the typical retirement home.
I don't think I'd like to do it though.