I dunno, the largest accidental AWS overages I’ve triaged in my career (at very different companies) were all storage. Dangling EBS, forgotten S3 accumulating data after a deletion cron broke, incompletely retention-policy’d CloudWatch buckets, Aurora snapshots…the list is pretty long.

“Large” is relative to the business of course, but the biggest storage-related overages I’ve personally triaged are in the high $100ks to low $millions per month. Colleagues have heard of orders of magnitude more costly.