One thing to mention is that DynamoDb and Postgres are vastly different databases, so the migration won't be a simple "dump and restore".

You're right - it will be a daunting task, but one that only becomes more daunting the longer you wait. If you make the migration to Hertzner + self-hosting (even just to pure Postgres), I'm certain you will see huge savings. It's hard to give exact numbers without knowing your workload, but feel free to reach out if you want to step through the numbers. We're not one-eyed about Supabase, but we feel that Postgres is a solid choice for your core-OLTP workloads. We love seeing more businesses adopt it. It's good for the ecosystem, and good for open source in general