The notorious hidden AWS line — hourly charge plus per-GB processing.
NAT gateways charge to exist and again per GB processed, on top of egress — a classic surprise line. Route S3/DynamoDB through free VPC endpoints. Compare the underlying egress on the cloud egress cost calculator.
Free NAT gateway cost calculator — gateway hours and GB processed to the monthly cost of one of AWS most surprising bills.
It charges twice: an hourly fee (~$0.045/hr, about $32/month per gateway) just to run, plus a per-GB data-processing fee (~$0.045/GB) on everything that passes through — and that is on top of standard egress. High-traffic private subnets rack up the processing fee fast.
Use VPC gateway endpoints for S3 and DynamoDB (traffic to them skips the NAT entirely and is free), consolidate to fewer gateways where HA allows, keep chatty AWS-service traffic on private endpoints, and for low-traffic cases consider a self-managed NAT instance.
Cost at different volumes:
| Volume | Monthly | Yearly |
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