It's a charity movie.
The movie itself is terrible. Awful. Unwatchable. Maybe it's just blank black screen. Maybe it's somewhat like Desert Bus in movie form. Maybe it cost a hundred bucks to make. The movie sucks. That's not the point. The point of the movie is that it is a charitable act. You buy tickets and then don't see it. You go to the cinema and buy two tickets, one for a regular movie and also a ticket to the charity movie running at the same time in a different screen. You stay to watch the first movie, and leave without seeing the second.
That's it. Most of the ticket price goes to charity. The DVD cost maybe 88p to manufacture and distribute; it's on sale for £15.95. It, too, is a charity thing. You buy it and most of your cash goes to charity. Meanwhile you get something basically worthless in return.