I think control is maybe a bigger factor than cost these days. Being able to hold anyone accountable at all seems to be an operational superpower. Working with cloud vendor support is a torturous experience on a good day. It also doesn't matter how expensive the virtual machine is if there isn't one available to be provisioned.
I know it's kind of harsh, but owning the whole vertical and having the power to instantly fire anyone for giving an Azure-tier response is why these companies are doing it in my mind. Waiting on a 3rd party to find their own ass with a whole S&R team every time you need help is quite exhausting. I've never worked with an IT vendor and thought "damn these people are so responsive I can't dream of doing it better myself".
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