Firebase is very good, yes, but I compared Firebase with other online databases such as PostgreSQL, Amazon AWS and MySQL. And Firebase Firestore was really extremely expensive compared to the other online databases. Especially AWS S3 was very cheap. I entered 50 operations per user per day as an example, with 100,000 users daily. And with Firebase Firestore, for example, the costs would be €180 per day and with AWS S3 €23 per day. So I don't know why everyone uses Firebase. Either I'm missing something or people don't know any better.
Yes Firestore for sure is more expensive especially when you look at the bandwidth limits. It's not a good choice for any type of video/ audio streaming app.
I'm not saying it's "worth it", but Firebase has guaranteed scalability (it doesn't allow certain queries that could eventually slow to a crawl as you accumulate data) and also supports offline mode (massively useful for certain apps). Just feel that comparing to Postgres/MySQL like that is comparing apples to oranges.
