AWS NAT Gateway is essential for managing traffic from private subnets, but it can silently inflate your cloud costs through data processing fees. Every AWS service call—whether to S3, DynamoDB, or other services—incurs a $0.045/GB charge when routed through NAT Gateway.

Back in the day, that makes me sound old but would you just not run an EC2 with iptables or something else that takes your fancy on?