You do not pay for an EC2 instance that is stopped. If the instance has attached EBS volumes you will continue to pay for the storage costs, but that is pretty minimal.
It is important to remember that a stopped instanced is not guaranteed to be able to be started again. If you have a m1.large stopped, there is a chance that Amazon will not have any m1.larges available in that zone/region when you try to start back up your instance.
Also know that the private dns name will change when a stopped instance is started again, so anything configured to point at that particular instance will have to be reconfigured.
I agree with allowing AWS to auto-provision N new instances when needed.
But from the article and with my financial hat on, when the large instance is stopped and left in a standby role, are you still paying for it?