I assume the 5G will be using the ship's Starlink as backhaul, but that's just an assumption I don't actually know how it will work.
The problem with cellular roaming on ships right now is it all goes over Cellular At Sea, an AT&T company (no matter who your carrier is), so there is no competition and thus rates are very high.
With Starlink offering near land speeds and reliability and 5G being more efficient, I would expect to see this 5G be more affordable than the current Cellular At Sea over time.