> Not underestimating at all. Of course it will be a lot
Do you have any data to back this up? Starlink (and other possible future constellations) most effectively serve the low-density or unconnected areas of the world. North America alone has a land area on the order of 25 million square km, with significant topographical and geographical contraints.
I have several relatives who had what the government considered "high speed" internet available - one an old adsl 1.5Mbit connection, the other a drastically overprovisioned cell phone wireless that they were lucky if it provided 0.5Mbit real world connections. The providers offered no consolation, and there was zero prospect of them upgrading services. Both relatives are now happily using their starlink at ~200Mbit.
> other forms of satcomms can be done with and order of magnitude less satellites.
There is effectively a per-satellite maximum bandwidth, as well as distance-based power requirements. The same satellite in low earth orbit can provide much better internet than if it were in GEO. Non-LEO satellites will remain second-class internet (with lower speeds and higher latencies) because of fundamental physical limitations.