Effect of Horizontal scaling / scale out on Azure App Services Pricing

I am following best practices document and trying to implement Auto Scaling and would like to know about pricing perspective. Robust-Apps-for-the-cloud

I would like to utilize custom auto scale to use multiple instances. I have configured the rules as shown here:

With this, I would like more information on how this will affect the pricing for my app service plan.

Note: My App Service Plan is S2.

App Service Plans are priced based on the size and number of instances you run, and they are billed on a per second basis. For your case on the S2 plan, a single instance will cost $0.20/hour.

I see on your autoscale configuration that the minimum and default number of instances you will be running on this plan is two instances. With this, if the autoscale triggers are not hit, your App Service Plan would cost $0.40/hour.

With the configuration you shared this could run up to $0.80/hour, if maximum four instances are run after the autoscale triggers are met.

As App Service Plans are billed on a per second basis, the cost will be prorated on a per second basis for the number of instances you run.

For example:

if you were running two instances for 40 minutes, three instances for 10 minutes, and four instances for the last 10 minutes of an hour. The total cost of the App Service Plan for that hour would be roughly: $0.50 for that hour.

If you were to scale up or down your App Service Plan tier you can see more information about how this could affect pricing using this tool here: App Service Pricing