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.
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.