There are almost certainly other services out there, but the advantage of Lulu is that you have a much wider audience. Sure, 50% is high, but it's better to have 50% of something than 20% of nothing.

As an alternative, you might want to consider finding a niche online retailer, i.e. one that only sells certain kinds of books. These can have a loyal customer base. But I wouldn't know if they're any cheaper.