@MSAzureAZ Confirmed from PG, this is not possible as of now, you will be charged when you turn on the Azure Defender.
You can submit a feedback for this at our page : https://feedback.azure.com/forums/347535-azure-security-center
For now, although MS does not recommend turning of AZ defender for resources, but as per your discretion, you can turn off the AZ defender for all resource except one which charge you least, something like this you can try different resource as well from list. You will need to test this setup and proceed accordingly.
-----------------------------------------------------------------------------------------------------------------
If the suggested response helped you resolve your issue, please do not forget to accept the response as Answer and "Up-Vote" for the answer that helped you for benefit of the community.