Choosing between managed and self-hosted database

The comparison that matters is not price per month:

Self-hosting wins on invoice and loses on the hours you cannot schedule. Below one full-time operator, managed is usually cheaper in the currency that runs out first.

At ten times the size the bottleneck moves from the operation itself to what it competes with: memory, locks and the people who have to run it. The approach stays, the batching gets smaller and the schedule matters more.