Person A and person B (or group B) want to communicate by using the internet

Idea: Use person C's website

This was never a good idea for A and B but turned out to be a great idea for C

C derives the benefit, C became a billionaire, but it is taking a very long time for A and C to realise they are not getting a good deal

Sadly in 2025 A and B believe there is no other way to communicate via the internet other than through C

C could disappear and the internet would live on, and A and B would indeed be able to communicate

A and B pay internet subscription fees, but generally do not pay subscription fees to C

The internet is worth something, people are willing to pay for it; C's value is questionable, few would be willing to pay for it

If not for the internet, C would not be a billionaire

If not for the internet, A and B could not communicate via C

The case for the internet is stronger than the case for C

s/A and C/A and B/

Yes, this. It's a symptom of late-stage capitalism.