Setup AWS High Available Autoscale Environment for Wordpress

I will move a wordpress website to AWS. It is using multiple plugins. Later on I'll transfer all my wordpress websites. I need to set up an AWS High Available Environment for Wordpress which should be : - autoscalable - support automatic installation of plugins through wordpress - be able to migrate other wordpress sites using file transfer and sql export - base configuration should be as cheap as possible (please mention your estimate of base/starting configuration cost)