What will I pay if I run multiple instances of the same android device image I subscribed on aws marktplace?

You pay $0.60 per hour per instance, plus any AWS marketplace and EC2 infrastructure fees. So running 5 instances for 1 hour costs the same Genymotion fee as 1 instance for 5 hours, because billing is per instance-hour.

• Genymotion states: “$0.60 / hour per instance, without Cloud platform fees” on the Device Image pricing page. Genymotion PaaS (Device Image)
• The AWS page confirms: “You are billed the same for using 1 Genymotion instance for 5h, or 5 instances for 1h.” Get to the Next Level with Genymotion on AWS

Are you estimating cost for a short test run or for a larger parallel testing setup?