For a fascinating counterpoint (gist: cloud hosted Postgres on RDS aurora is not anything like the system you would host yourself, and other cloud deployments of databases should also not be done like our field is used to doing it when self-hosting) see this other front page article and discussion: https://news.ycombinator.com/item?id=46334990
Aurora is a closed-source fork of PostgreSQL. So it is indeed not possible to self-host it.
However a self-hosted PostgreSQL on a bare metal server with NVMe SSDs will much faster than what RDS is capable of. Especially at the same price points.