This isn’t 100% true. Social medias become much more valuable due to a network effect, and non-paying users add to the overall network of potential interactions and content.

Imagine a scenario where there is a single road leading to your business. You pay to maintain the road, with the help of a few charitable people who really love your business. But the vast majority of people who use the road get to use it for free. It’s still incredibly valuable for you to have those people there - that’s why you’re ok with eating the costs of the road.

Obviously this economic model is much more complicated than that simple example, with relays, clients, and users all being different economic actors (most of the time). But it is possible to have an equilibrium where everyone profits and a vast majority of people still use it for free.