Running an AppView for your own app is not expensive at all. It can be as cheap as you want. It's only expensive if you want to store gigabytes of Bluesky posts and serve them to millions of users — i.e. if you want to build the full Bluesky AppView. But why would you want to build a Bluesky AppView? That's part of what I'm alluding to in my article — atproto isn't "for Bluesky". You can build any social app.
The problem is that that sounds like "you shouldn't want to compete with Bluesky". Which makes it dangerously centralized.
I like the concept of working like RSS. I don't like the idea of having a massive ecosystem coordination problem with game-theoretic network effects, for any component of the system.