This is how I've been thinking Lemmy can scale. Sync can host their own instance funded by premium subscribers. In other cases, a group of friends with common local interests can host an instance with their local channels plus caching posts on other instances, and peoppe could connect to that or lemmy.world for free and see the same content.
I did ask them about this in the Discord server, but they aren't planning on this. Apparently, the cost would be quite a bit higher than the subscription, and they wouldn't be profitable. They are keeping it open for the future, if it becomes easier to monetize, but they don't have any plans for it as of right now.