But one could just have two categories of service - the default capped plan, and a special Enterprise one where you sign a contract making it clear you understand the consequences of not having a budget limit.
Also, if your average usage is $900, set your hard limit at $2,000, not $1,000. Then when the report runs $500 over expected, you get a soft limit email and still have your report. Even a "business critical" run is probably not actually worth more than double your average spend.