We're just comparing the Amazon Web Application template as provided in their calculator, with no changes.
You're right that it is x2 for each EC2 server which I didn't notice until later, but that doesn't change the economics or performance story very much.
Yes, we're comparing the web application template as provided. Except you compared less than half of it instead of comparing it. I think "I claimed that AWS is twice as expensive as it actually is" certainly changes the economics much. Your 3 servers is not 6 servers and a load balancer. Reliability counts too, not just performance. Especially since most web apps are going to be 90% idle on the AWS hardware.
You're right that it is x2 for each EC2 server which I didn't notice until later, but that doesn't change the economics or performance story very much.