You're spot on that Aurora is super-powerful for performance and scaling, giving it characteristics and controls that don't really exist elsewhere. I heard a great talk with their engineering lead about how they optimized Postgres internals to play nicely with S3.
I still think a small Aurora Postgres with some workday scaling events on a schedule would have more affordable and predictable if the bulk of the workload is 9-6 weekdays. Serverless Aurora is (finally) great, but expensive and really requires some extra work to optimize usages to minimize cost.
