It costs them more to serve these resources to you. They're not obligated to deal with customers whose use of the resources goes beyond the ordinary or regular.
Look, I don’t know what’s so hard here. If you sell cloud compute it should be on the basis of usage. If that usage is 100% then charge aptly.
Just don’t market yourself as an open and non limited compute resource charged by usage.
Market yourself as a QOS’d, shaped sub service.