A thing that scares me is anyone saying they're running their own HA cluster (not single instance) for cost reasons. Infra people are not cheaper than the hosted solutions (Amazon RDS, Google Cloud SQL, Heroku Postgres).
That’s a blanket statement that has very little basis in reality. Hosted Postgres is never going to give you the performance you need for low latency deployments.
My claim is that you need to hire some expensive people if you want that performance, not that there aren't reasons to run your own database instances!