A theme of many of the horror stories is something like "I set up something personal, costing a few dollars a month, and I was DDOSed or (in earlier terms) slashdotted out of the blue, and I now have a bill for $17k accumulated over 4 hours".
As someone else pointed out, some(?) services prevent unlimited autoscaling, but even without unlimited, you may still hit a much larger limit.
Being able to say 'if my bill goes above $400, shut off all compute resources' or something like that. Account is still on, and you have X days (3? 1? 14?) to re-enable services, pay the bill, or proceed as you wish.
Yes, you might still want some period of high $/sec, but nearly every horror story in this vein ends with an issue with the final bill. Whether I burn $300 in 5 minutes or 26 days, I want some assurance that the services that are contributing most to that - likely/often EC2 or lambda in the AWS world - will be paused to stop the bleeding.
If you could pipe "billing notification" SNS message to something that could simply shut off public network access to certain resources, perhaps that would suffice. I imagine there's enough internal plumbing there to facilitate that, but even then, that's just AWS - how other cloud providers might handle that would be different. Having it be a core feature would be useful.
I was on a team that had our github CI pipeline routinely shutdown multiple times over a few weeks because some rogue processes were eating up a lot of minutes. We may have typically used $50/$100 per month - suddenly it was $100 in a day. Then... $200. Github just stopped the ability to run, because the credits used were over the limits. They probably could run their business where they would have just moved to charging us hundreds per day, perhaps with an email to an admin, and then set the invoice at $4500 for the month. But they shut down functionality a bit after the credits were exhausted.