Your math is way off. 50M subs with the coverage over land and total bandwidth will put their provisioning rate (Bps/sub) way below even the Geo satellite providers. They need to charge a lot more or provide slower service by having more people.
And that’s assuming next generations will not improve downlink speeds. It does assume satellites would be fully utilized which is wrong unless we populate the oceans, but that’s the theoretical max.
That's the entire point. They're mostly over the ocean/areas without high-paying customers 70-90% of the time. Because of that, it would be more like (in the best case):
42k sats@20G * 0.2 * 5 million subs target = 33Mbps/sub. However, that's not even close to realistic either because the high-paying subs are in the US and parts of Europe only, and you can't keep piling 42k satellites in the same plane. So in reality, that will be cut significantly from that.
