Patri Friedman and the Seasteading Institute is pushing the idea of “of autonomous, mobile communities on seaborne platforms (“seasteads”) operating in international waters.”
I can see some problems with the idea. The first is that the group, as far as I can tell from its site, is not very aware that they are reinventing the flotel (floating hotel) or accommodation platform. Building and selling or renting these is already a multimillion dollar industry. Workers on offshore oil rigs need a place to sleep and spend their off-duty time, and flying them home every night is not cost effective.
The good news is that there is already an established industry offering mobile platforms of 600 berths or more, and fiercely devoted to making them available at the lowest possible price. The bad news is that the lowest possible price isn’t very low. Leased accommodation platforms seem to run about $6-15 thousand a month per berth, not counting insurance, fuel, resupply and catering expenses, for contracts ranging from 6-24 months in length.
A platform devoted purely to accommodation would probably cost a bit less, since the accommodation platforms serving the oil industry often devote space and tonnage to cranes, workshops and deck space for other support functions. I’d be surprised if you could cut the cost per berth by more than 50%, however.
Given that you might be able to buy a single berth on a cruise ship for $3-6 thousand a month, this seems high at first glance. However, cruise ships probably benefit from economies of scale: 600 berths is large for an oil industry flotel, but very small for a cruise ship. Cruise ships can sail around the worst storms, but a nearly immobile platform must be able to survive storms a more mobile ship can evade.