If your AWS bill has a NAT Gateway line, you are paying twice for the same packet: once for the gateway to merely exist, and again for every gigabyte it carries. The fix for most teams is dull and free. Add an S3 and a DynamoDB gateway endpoint, route the heavy traffic away from NAT, and only then argue about anything fancier. That single change is free to turn on, takes minutes, and stops the most expensive traffic from ever touching the meter.
This is a playbook, not a lecture. The trick with NAT Gateway pricing is that the two charges hide in different places on the bill, so most teams only ever see half of it. Numbers first, then the fixes, in the order I would actually do them.
What you are actually being charged for
NAT Gateway has two charges, and people forget the second one until they read the bill closely.
Hourly charge — you pay for every hour the gateway is provisioned and available, whether or not a single byte moves through it. In us-east-1 (N. Virginia) and us-east-2 (Ohio) this is $0.045 per NAT Gateway-hour. That is roughly $32.85 a month per gateway just to keep the lights on. Partial hours bill as full hours.
