They are just insuring against an unexpectedly large bill. That's how I read it. It doesn't even have to involve any proof or disproof of negligence. Just make it a purely financial transaction. You pay $1,000 as a premium such that if the cloud bill exceeds $10,000 the insurance will pay you half of that, up to a limit of $20,000. It makes sense as a financial product. Of course the numbers above are purely hypothetical.
Just because it's possible to state a hypothetical financial product does not mean there's a useful product there.
Why would I agree to pay up to $20k on a $50k cloud bill, when you could just choose to spend more on your cloud bill. I would be giving away free money and you'd get a discount.
You have to tie it to either incorrect billing, valid billing but caused by a malicious third party (i.e. hacking), or valid billing caused by negligence, and in the latter case you would need to prove negligence otherwise it's just a business deciding to use more resources and not pay for them. In the same way, fire insurance covers your house burning down, but not if you burn it down yourself.
Such insurance likely would require documenting full due diligence and being able to prove that you followed all instructions and known best practises at time of incident. Which likely would get the insurer out of most cases...
