One of the biggest problems with the self-hosted situations I’ve seen is when the senior engineers who set it up leave and the next generation has to figure out how to run it all.

In theory with perfect documentation they’d have a good head start to learn it, but there is always a lot of unwritten knowledge involved in managing an inherited setup.

With AWS the knowledge is at least transferable and you can find people who have worked with that exact thing before.

Engineers also leave for a lot of reasons. Even highly paid engineers go off and retire, change to a job for more novelty, or decide to try starting their own business.