Most S3 bills are wrong, and the fix takes an afternoon. The data sits in the most expensive class AWS offers (S3 Standard, $0.023/GB-month), nobody set a lifecycle policy, incomplete multipart uploads are silently billing for storage you can't even see in the console, and every byte your EC2 fleet pulls from S3 is routed out through a NAT Gateway when a free VPC Gateway Endpoint would do the same job for $0. None of this needs an architecture rewrite. It needs a checklist run in the right order...