I can see this being how they monetize it.
I think it will be difficult to ever charge for the SOS satellite feature, as they’ve done it for free for 2 years now. And people are unlikely to pay for something that most will never use, even if the benefits when you use it are huge.
But they could charge for the messaging feature, which could support the entire satellite part of the business. I’d they ever could get to photos, that would be huge, as people could be in contact all the time
Of course, breathing down their necks (or nearly, the necks of the carriers, not a Apple so much) is the T-Mobile/Starlink deal to allow phones to use their regular antenas to connect to Starlink. That would partially displace cell towers, and given the number and low elevation of Starlink satellites, could much more easily allow photos and even phone calls, and perhaps eventually video and slow internet usage. A much more robust, and easier to use, system them Apple. And given that SpaceX effectively subsidizes Starlink by using old rockets and ad an opportunity to get rocket experience and reliability, it’s hard to see anyone else competing in that space in the next decade. But it would work with iPhones (and most phones) on TMobile, so it wouldn’t directly undercut Apple.