Location, location, location…
Big difference in costs for every single land-based import is going to be the fuel and infrastructure to import everything.
Exports will also face the same issue.
A ‘small’ seastead will obviously handle this differently, but loading/unloading from a cargo vessel will require an awful lot of that capacity.
International waters, 200 NM out makes for an unbelievable cost increase, as demonstrated by the lack of mega-container-ship capacity in Hawaii, covered in other recent topics.