Oof. I have a very similar set up except I'm using their managed MySQL instead of PostgreSQL. It appears I wasn't hit.

Same thought as you.. I just didn't want to figure out and manage MySQL-with-failover myself so I switched their managed solution a year or two ago and my bill went up like 300% or more (was running fine on a ~$12 or maybe $24 droplet + $5 volume but now costs, I don't even remember, $150 or so).