> Whether you’re rich or poor, Facebook costs the same and the experience and features you have access to are identical.

Or you can say, the amount of work that's extracted from the user is the same. Because the major "service" of social media isn't the webapp that has a feed timeline, or a fancy UI, or availability (which can be easily copied by competitors). It's the network effect that comes from user's participation. It's very possible there's a net profit for the majority of users (either from clicking the ads, or from simply using the social media), so the "subsidized" users' loss is not a primary concern here.