I have the same configuration and running it for almost a year. There is no dedicated Backup and Recovery cost dashboard in BlueXP Cloud Manager. Backup and Recovery charges are reflected directly in the Azure subscription, not in Cloud Manager itself. To see the actual costs, you need to check:
Azure Cost Management + Billing for your subscription
Filter by Azure Blob Storage (the backup target storage account)
Review storage consumption
Cloud Manager shows backup status and protected capacity, but billing and usage costs are visible only in Azure, under the storage account used for the Backup vault.
Overall, it is in Azure billing. You will see it there.