Operating and administering your own systems infrastructure requires that your business invest in the people to do so, this builds institutional knowledge which makes the important bit, the data and knowledge, portable. If the VM in the cloud gets too expensive you can use another provider, or you can buy hardware and run it locally. If the VM provider cuts your service you still have access to your data because you never lost control of it. Problems can be fixed by in house staff that don’t suddenly evaporate for arbitrary reasons or have service outages.

If your entire business depends on Microsoft services and it gets too expensive you have no options but to pay more. If your account gets locked then you’re out of business until you can get Microsoft to give you access again. If you want to migrate away, there isn’t another Microsoft to move your data to and you’ve replaced all of your technical staff with a support phone number, which isn’t currently accepting your calls.