As i understand AWS is that you Pay for active Time, so if you had a constant stream of 20kb/s it was running 24/7.
AWS works good when you have an Application that only gets used for like a Few Seconds and then doesnt Stream any Data or Computing somthing.
A Friend of mine uses AWS to get Some Informations like a list of links for his APP and then the AWS instance is Sleeping again and it doesnt cost more then a few cents a month or so.