Beyond the usual points there are some other important factors to consider self-hosting PG:

1. Access to any extension you want and importantly ability to create your own extensions.

2. Being able to run any version you want, including being able to adopt patches ahead of releases.

3. Ability to tune for maximum performance based on the kind of workload you have. If it's massively parallel you can fill the box with huge amounts of memory and screaming fast SSDs, if it's very compute heavy you can spec the box with really tall cores etc.

Self hosting is rarely about cost, it's usually about control for me. Being able to replace complex application logic/types with a nice custom pgrx extension can save massive amounts of time. Similarity using a custom index access method can unlock a step change in performance unachievable without some non-PG solution that would compromise on simplicity by forcing a second data store.