When I was with Royal Caribbean / celebrity, I was in charge of a group of devs that developed the software for everything you purchase before the cruise (drink packages, dining, shore excursion, etc) and that software also ran on ships just for shore ex.
I left it in 2012 and we were bringing in $1.8b just from those units on ~30 ships. Reservations, casino, and drinks onboard were the other money makers.
It’s big big money, and it has been stagnating for a year... more if you include future cruise planning.
Actually that 1.8 number was just precursor through credit cards. It didn’t include onboard shore excursions.
The islands have to be absolutely in a depression from the lack of cruisers