@Shiva Kakileti
If you look at Cost Analysis in Cost Management you should be able to see the number of transaction being performed. With the costs you are seeing I am guessing you have a very transaction intensive workload. Your analysis is correct in that premium shares would be cheaper on the surface. However premium shares performance scales based on provisioned size and the minimum size to provision is 100GiB. It still would likely come out cheaper even if you had to overprovision the premium file share. All costs should be displayed on the Azure Files pricing page.
Hope this helps! Let us know if you have further questions or concerns and we will be happy to assist.
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