I don't know about the others, but AWS is not free and it's not cheap. There are ways to set alerts on budget overruns, but there is no foolproof way to limit monthly spending. Eventually you will configure something that goes out of control, or I was able to conceive of a few scenarios where a malicious third party could rack up charges for, e.g. S3 egress costs. Good luck contesting the charges more than once. I shut everything down and pulled out of AWS. I believe that Azure's free trial featured a hard cap, but still requires a credit card to open your account.