Effective October 25, 2024, all CloudFront requests blocked by AWS WAF are free of charge. With this change, CloudFront customers will never incur request fees or data transfer charges for requests blocked by AWS WAF. This update requires no changes to your applications and applies to all CloudFront distributions using AWS WAF.
AWS WAF will continue billing for evaluating and blocking these requests. To learn more about using AWS WAF with CloudFront, visit Use AWS WAF protections in the CloudFront Developer Guide.
Source:: Amazon AWS