I created a few VMs in my Azure Free Trial subscription about a week ago to experiment with. I checked up on the charges today and noticed that I was being charged for the disks that were created along with the VMs. (I believe these are what is referred to as "managed disks", although the invoice just calls these "disks".)
When I create the VM, I am given a choice of Premium SSD, Standard SSD, and Standard HDD for the disk. So it seems that in addition to the costs of having a VM, one has to also factor in the costs of the disk that a VM has. Is that correct? It seems like charging a hotel guest for the bed in addition to the room rate to me.
You don't need to have disk if you are trying some proof of concept and it can fit with temporary storage that comes with VM Otherwise you can add "data disk" while creating VM or later Also regarding cost, MS document says "Storage costs are charged separately for the Azure Storage used by the virtual machine. The status of the virtual machine has no relation to the Azure Storage charges that are incurred. You're always charged for any Azure Storage used by the disks"