Is there any special techniques on running SaSS apps? I know some people use EC2 and then charge on top of that. What are the problems or techniques when doing this?
If you have objects or services that customers want repeatedly it may be advantageous to store the objects in S3, deploy the services from EC2, secure them via authentication/obscurity and charge in proportion to demand using DevPay. Without knowing anything about your application, this generic AWS approach seems as good as any.