Interestingly, there are two stages of any project when self-hosting is way more efficient. First is an MVP stage, when you do it on a single VPS for $5/month

Interestingly, there are two stages of any project when self-hosting is way more efficient. First is an MVP stage, when you do it on a single VPS for $5/month + $1 for backups. Second is multifold scaling stage, when you rent or even buy a couple of cabinets of bare metal hardware. BTW, AWS Postgres does not support master-master replication, which makes no-downtime migration pretty hard. Just remember about those small quirks making vendor lock stronger.