Considering the coverage map is mostly coastal waters, private LTE and 5g are the 'budget' competition (for now). In some areas like the Gulf of Mexico, a not insignificant portion of the water is serviced by LTE that you can roam onto using a conventional TMobile, Sprint or AT&T SIM, often without an additional cost.
Agreed, currently it does not seem to be competitive (Inmarsat also offers significant discounts on their coastal plans for the same reason). But with their projected coverage in Q4 2022 and Q1 2023, it's a very different story.
