The S3 buckets are private and we haven't been doing anything in the accounts which would lead to these billions of scans. We do have a widely deployed SaaS tool in the account but I don't think that would do it either.
What has annoyed me is the attitude of their support. They just say they've looked into it and they won't reverse the charges and because logging wasn't on at the time I am out of luck. They don't appear to be willing to negotiate.
Being reasonable, I'm sure this comes from an error on our side rather than billing error, but we are completely in the dark what could have caused it so don't think we should be completely on the hook.
I always thought of AWS as quite customer centric and heard they were helpful in these situations, but guess they are getting big enough to start engaging in this Oracle like behaviour.
Each billion LIST requests will cost $5K at retail pricing, for those wondering.