There is no additional cost for these notifications. You pay only for the underlying resources, such as CodeCommit, CodeBuild, CodeDeploy, CodePipeline, and standard SNS charges. To learn how to get started with notifications, see the notifications user guide. Additionally, customers using AWS Chatbot can configure notifications to be sent to their Slack Channels or Amazon Chime chatrooms. For more details please visit here.
You can see a full list of AWS Regions where the notification feature is available here.