For a million 2-hour movies, stored at 10 mbps, (plus another 10 mbps for other versions), you end up with 18 petabytes. That can be stored on S3 for $396k per month, or on 200 180TB backblaze storage pods for a $1.8M one-time cost, plus $30k/mo for 20 full racks somewhere cheap. I assume bandwidth costs would be manageable either way, since the vast majority of these films are going to be accessed very rarely.
Just back-of-the-envelope calculations from someone who hasn't worked at this sort of scale. If I'm off by an order of magnitude then it'd be impractical to store on S3, since the fees would be something like 1/4 of their current profits.