Number of Windows licenses (RDS SAL) required for AppStream

For your AppStream 2.0 setup with Windows applications, you would need to pay for 100 user fees, not just 10. The Microsoft Remote Desktop Service Subscriber Access License (RDS SAL) fee is charged per user per month in each AWS Region where users stream applications from AppStream 2.0 fleet instances, regardless of how often they actually use the service or how many concurrent users you have.

The fee is $4.19 per user per month for single-session fleets or $6.42 for multi-session fleets. This means that even if only 10 users are connecting concurrently, you would still need to pay for all 100 registered users who have the potential to access the service within that month.

However, there are a few options that might help optimize your costs:

1. If you're an educational institution or certain type of public institution, you may qualify for a reduced Microsoft RDS SAL user fee of $0.44 per user per month.

2. If you have Microsoft License Mobility, you might be eligible to bring your own Microsoft RDS Client Access License (CAL) licenses and use them with Amazon AppStream 2.0. In this case, you wouldn't incur monthly user fees for users covered by your own licenses.

3. Consider using a non-Windows operating system for your fleet instances. Streaming from fleet instances that use Rocky Linux, Red Hat Enterprise Linux, or Amazon Linux operating systems does not incur user fees.

4. If your use case allows for it, you could explore creating temporary streaming URLs for specific users instead of assigning usernames and passwords. This approach might be suitable for short-term or trial access scenarios.

Remember to consult with your AWS account team or a licensing specialist to ensure you're choosing the most cost-effective and compliant option for your specific use case.
Sources
Non-Persistent Desktops and Applications - Amazon AppStream 2.0 Pricing - Amazon Web Services
Cost optimization - Best Practices for Deploying Amazon AppStream 2.0
Appstream2 : How to save User fees | AWS re:Post