If the degraded or offline system is used by people, and these people cannot work, the cost can be a lot higher. For example, 10 people not able to work could cost something in the range of $250-$750 per hour.
Moreover, if customers are lost due to this degradation of service and CAC is high, then clearly the cheapest thing is a high bill by AWS, which probably is also capped by Amazon (and handled as an alert by Amazon).