Billing alerts can tell you exactly when you have spent 4 figures after the fact. Using a VPS prevents 4-figure bills.

Actual billing caps are very hard for cloud providers to implement with the HA distributed systems clouds use for billing, and would carry a significant performance cost. Alerts are the best you can do if you take the variable costs.

Thanks for explaining that. I didn't think about the complexities of billing caps. Is there a contract from a cloud provider that even if they do go over the billing cap, since you set that as your "limit", they can't bill you for over that amount? I imagine that the responsibility for managing billing caps lies on the provider, and the consumer should be comfortable that they will not be charged above the limit they set.