You can enable Local Zones without any additional fees. You pay only for the services you consume in Local Zones.
AWS Services in Local Zones
Amazon EC2 Instances and other AWS resources in Local Zones will have different prices than in the parent region. There are three ways to pay for Amazon EC2 instances in Local Zones: On-Demand, Savings Plans, and Spot Instances. Learn about the prices for EBS, FSx for Windows, FSx for Lustre, ELB, EMR, and RDS.
AWS Marketplace Software
You pay the same price for AMIs and services purchased from AWS Marketplace as in the AWS Region.