Thank you for reaching out to the Microsoft Q&A platform.
Azure Container Apps on Azure Arc enabled Kubernetes is free of charge during preview. This means that you will not be charged for using Azure Container Apps on Azure Arc enabled Kubernetes during the preview period. However, any Azure service that is used on Azure Arc-enabled Kubernetes, such as Microsoft Defender for Cloud or Azure Monitor, will be charged as per the pricing for that service.
If you are using any of these services, you will be charged for their usage. If you are not using any of these services, then you will not be charged.
You can learn more about Defender for Container's pricing on the pricing page.
If I have answered your query, please click "Accept as answer" as a token of appreciation