Well, the sub part is pretty expensive, since you have to accomodate 100+ people, with a nuclear reactor/diesel engine + batteries and all the supplies for a lo

Well, the sub part is pretty expensive, since you have to accomodate 100+ people, with a nuclear reactor/diesel engine + batteries and all the supplies for a long trip. And they need to be able to move undetected, that's the point of the nuclear missile sub as a strategic deterrent.