Hello @Julie M ,
Thanks for posting your query on Microsoft QnA.
As you mentioned you have 2 VMs/session hosts in your hostpool and 5 users are provided access to it, and you are seeing the cost from December to January has increased by almost 5 times. This can be because of the usage of the session hosts. If the sessions hosts are in running state for longer hours then it will accordingly consume the underlying infrastructure costs.
You can ask the users to log off properly from the session hosts once their work is done, or maybe apply a policy in place that will automatically log off users at a certain time of the day (non-working hours). Also, you can stop the VMs during the non-working hours to incur less infrastructure charges.
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