I pay $20/month for access to the servers and infrastructure. I get $10 of that to use as purchasing credit. Movies cost anywhere from $1-$5 depending on popularity, and the company buys them back for some small amount.
The company would probably need to have some system in place for dealing with people that actually want the DVD that they 'bought'. Maybe something as simple as letting people know that they own the DVD, but the company is not responsible for shipping it to them. If the customer wants to come pick it up at the office, he can feel free to swing by and have someone pull it from the data center for him.