I wouldn't switch from Vercel just to save X% per month, because the real cost was all the extra time to build and maintain the infrastructure myself. The savings never justified the hours.

With agents that math changes. The build and maintenance work moves onto the agent, so the savings threshold where switching makes sense drops a lot.

On top of that there are other goodies. Vercel is serverless, so you can't co-locate the API with the DB, which means extra latency and yet another bill (Supabase?). That's one more thing you can now own for basically no effort.

It's actually why I stopped at Railway level instead of going full VPS.