The notorious hidden AWS line β hourly charge plus per-GB processing.
NAT gateways charge to exist and again per GB processed, on top of egress β a classic surprise line. Route S3/DynamoDB through free VPC endpoints. Compare the underlying egress on the cloud egress cost calculator.
The NAT Gateway Cost Calculator estimates the monthly bill for running NAT gateways in a cloud environment such as AWS. It combines two cost components: a fixed hourly charge for each gateway you keep provisioned, and a per-gigabyte data processing charge for all traffic passing through it. You enter the number of gateways, the price per gateway-hour, the volume of data processed each month, and the price per gigabyte. The tool multiplies gateway-hours across the month, adds the processing cost, and returns a monthly total. The main drivers are simply how many gateways run and how much data flows through them.
This matters because NAT gateway charges are among the most frequently underestimated line items on a cloud bill. The per-gigabyte processing fee applies to every byte, including traffic to services in the same region that could often bypass the gateway entirely. Running one gateway per availability zone multiplies the fixed hourly cost. Before deploying, model your expected data volume here, and consider whether VPC endpoints for high-traffic services like S3 could route around the gateway and cut processing charges substantially.
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 β 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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