Final answer:
An unnecessary expense in Azure is having unused virtual machines that continue to incur charges even when not in use. Deallocating or deleting unused VMs and using automation to manage resources can reduce costs.
Step-by-step explanation:
One example of an unnecessary expense in Azure is Unused virtual machines. When a virtual machine is not in use but still running, it continues to incur charges because Azure charges for the compute resources it reserves, not just when those resources are actively being used. To avoid such expenses, you should deallocate or delete virtual machines that are no longer needed. Additionally, implementing automation to shut down or scale down virtual machines during off-peak hours can lead to significant cost savings.