At the end of the day -unless you really know how many tech/human resources something like netflix needs- you could wrongly asume a few guys could host the content on AWS, use a third party for billing and be done with it.
Looked into AWS a while ago so I could throw some encrypted containers on it thinking it would be cheaper. Storage on S3 would have cost about four times as much as I'm paying now in VPS costs, and EFS (the service I actualy wanted) about ten times as much, and that's before looking at bandwidth. Oh and I'd still need at least one VPS to handle transcoding, content delivery etc.
I think Netflix save money by using S3 for the majority of their storage but having their own CDN so they use less bandwidth from AWS.