That's a valid concern and I fully understand your thoughts her.
When discussing cost savings in terms of AWS bills, it's essential to consider that the potential savings here may not be negligible. Depending on the size of your organization, you can operate the services with relatively small container configurations, resulting in significantly lower costs compared to using managed services. However, as you rightly pointed out, this is only one aspect of the equation. Self-hosting does come with its own responsibilities and requires some effort on your part.
That said, I can share some of our experiences with our setup. We've been self-hosting all DataHub dependencies, with the exception of Kafka, as we already had MSK in place. Over the past 9 months, we haven't encountered any issues with these components; they have been performing reliably.
It's worth noting that there may be situations where you need to become familiar with the components, particularly when it comes to tasks like securing the traffic between Elasticsearch nodes.
Hope this helps you for your considerations. Perhaps replacing the most costly service with a self-hosted solution could be a viable option?