@Varsha Zutshi - Welcome to Microsoft Q&A and thanks for reaching out to us.
Yes, you do need the service account bearer token because Arc Kubernetes resource provider in Azure needs to authenticate and communicate with your Kubernetes cluster to retrieve workload info. In terms of billing, there's no cost to see the workload info in Azure Portal. It's only if you add security, monitoring, compliance, or other services on top of the workload that cost is incurred.
Please find more info on cost:
Hope this helps. and please feel free to reach out if you have any further questions.
Please don't forget to "Accept as Answer" and click "Yes" if the above response is helpful, so it can be beneficial to the community.