You're right, if we manage our own db, then we need everybody to understand how to troubleshoot across both software and hardware issues, rather than just file a ticket and follow instructions/suggestions.

Let's say we have 5 engineers and that kind of training costs us 1 hour per eng/per week. That's 20 hours a month, which is easily more than $1k/month and the cost grows as the team expands. This is before you account for the losses of having your own engineers on call for issues and setting up early warning systems specific to the database etc.