Security in LEO will eclipse the cost of everything else. Right now it’s free. When it becomes critical infrastructure, it has to be protected.

Security in outside plant isn't free either. We're a long way away from widespread outages because someone thought they could get high with the proceeds of a stolen satellite, but there are lots of disruptions when people take down pole mounted fiber because they thought it would be worth something.

But wires aren’t the only terrestrial option.

I can’t fathom how many satellites it would take to support all the internet users as a monopoly.

Fair enough; I didn't read your comment very closely, I guess. Terrestrial radio seems a lot less expensive in areas with population. When you get out beyond rural and more into wilderness, satellite is likely cost competitive, because having a LEO constellation cover the wilderness comes at no additional cost, and having radio coverage in the wilderness involves setting up base stations with low usage --- you can do some things with longer range / larger cells, but it depends on terrain and maybe protocol limits? GSM had a concept of 'timing advance' that effectively limited the maximum cell size, but I don't know if that's a limitation if you're not using TDMA.