Sure, there's a lot of potential customers but:

a) no one pays $100 for internet. Maybe some in monopoly-internet USA have to, but literally no one else.

b) most countries are poorer than the US and would definitely not have $100.

c) Local providers can simply lower their prices, and SpaceX will have competition from Oneweb and possibly others.

700 million people parting with $100 USD per month seems pretty high

Think any company with remote assets it needs to monitor.

Drones, backup internet etc. There's a very big market for fast internet access which just works anywhere on the planet. It would be worth a premium just to let large organisations consolidate to a single biller.

Sure, I can buy the end revenue stated, just not the implication that 700 million end consumers is the way to get there.

I was just using the 10% number posited by the OP