And yes, I think typically orgs. today are using SQL Server or Oracle for these databases.
There's this thing I wish existed but AFAIK doesn't: a guide that shows computer people the relative salaries of a bunch of different specialties. So people who have one specialty but would enjoy something else can see what the salaries are like.
Glassdoor is a very rough start on this.
For postgres itself, make sure you know what all the settings in the configuration means, why they make sense 90% of the time and definitely do not make sense in 10% of the time (such as a low memory server with super-fast SSD disk arrays). And in general ofcourse a good knowledge of SQL, index usage/performance. Postgres extensions (arrays, JSON, etc.) are decent, but in my experience it's something you can get into relatively fast if you are solid on the rest.