Storage capacity is billed in units of the average daily amount of data stored, in gigabytes (GB), over a monthly period. For example, if you consistently used 10 GB of storage for the first half of the month, and none for the second half of the month, you would be billed for your average usage of 5 GB of storage.
If your data is persistent in Azure Files you will be charged for as long as that data exists in the storage account. If the data is removed from Azure Files when you tear down your cluster you will only be charged the prorated cost.
Hope this helps. If you still find any difficulties in pricing/billing, Free billing and subscription management support is provided. The Billing and Subscription team would be the best to provide more insight and guidance on the pricing.
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