We know a densely populated land area can saturate the satellites overhead; it's part of the reason we don't use Starlink in, say, NYC. The same math applies to a thousand cruise ship passengers trying to use it at the same time.
(It will absolutely be much better than the previous state-of-the-art, though.)
Only recently (2025) has Starlink been documented to pass data between satellites and only for new ones. Cruise ships have had starlink for several years so the most common case will likely still be a single hop. Most cruises hug closely enough to the shore (within 100 miles) that a second hop isn't required.
It's not really a thousand passengers, it's just 12 terminals. Sure, those terminals are well oversubscribed vs a normal user terminal, but given the documented terminal-to-ground-station ratio (quite high), I'm pretty doubtful a cruise ship or 2 significantly impacts (or is impacted by) ground bandwidth. The density of users is just at the wrong scale for it to be significant.
Apparently a mid-size ship will have 12 terminals. That same thread talks about other ship sizes but not if they have more terminals.
I still submit that the pricing is entirely a function of what the market will bear, and not the cost of the service.