What exactly do the studios consider acceptable sales on a season release for them to continue? Is there a magic number they look to hit? Also, do they have any knowledge of their product? For instance, I'm not a Mary Tyler Moore expert but I do know that many fans of the show like the later seasons much more than the first and that those might sell better. There are other shows with similar stories where the show did not hit its stride until a couple of years in. But since all shows seem to be issued in order, what about a show who's initial season wasn't that good and which doesn't sell well. Do they then not issue further sets even though they would be more popular?