This article details how pricing works for SFTP Gateway on Azure marketplace. It goes over pricing, and how to stop your service.
Pay as you go Pricing
SFTP Gateway VM uses pay-as-you-go pricing, this means that you are charged a flat rate of $0.06 per hour for the software when you are running it. This pricing applies to the software only, there is a separate charge for the infrastructure and hourly cost of running your specific VM which varies depending on the VM. Also, the price remains the same regardless of the number of cores the VM has.
The cheapest instance that the SFTP Gateway can run on is
B1ms VM which
charges $0.03 USD per hour. Running both the SFTP Gateway software and
VM amounts to around $65 USD per month, if the VM is running around the
clock. Also, this does not include Blob storage costs, as although Blob is cheap, the
costs may add up since data can grow indefinitely.
How to stop being charged
When you want to stop getting charged for the product, you stop/deallocate the VM. The same also applies to the VM hardware, you are no longer charged when the VM is stopped. If you have multiple VMs running at the same time you are charged with an hourly rate for each VM as long as they are running. If you have multiple VMs using SFTP gateway but only one is running at that moment you will only be charged for that single running VM.