Wow! Talking about mixing things. First off, blank DVDs and commercial prerecorded DVDs are very different media. Your example of District 9 can take us on several different tangents. Let's deal with one. The movie was not direct-to-video. I don't know how much it made in theatrical release. However, I assume that the theatrical release was profitable. If this is the case, then the DVD is simply additional revenue. The additional revenue is used to enrich the distributers, producers, actors, and to subsidize other projects that may or may not be so successful.