Could you walk me through how to estimate AWS costs for this setup?
You pay Genymotion and AWS separately. Genymotion charges depend on the subscription plan, and AWS charges depend on the EC2 instance type and cloud usage. How will I be charged for Genymotion on Amazon Web Service (AWS)?
For an estimate, use the AWS Marketplace pricing page linked in the article: AWS Marketplace seller profile. If you use the hourly plan, billing rounds up by hour, so 1 to 60 minutes is billed as 1 hour, 61 to 120 minutes as 2 hours, and so on.