No, because the fact that there is so much self-published crap is why I, and I expect many other authors, have a problem with it. I don't buy self-published books because I know it's extremely likely I'll be disappointed, and I won't self-publish a book because how can I expect anyone else to wade through slush to find mine? If you take out the most problematic element of self-publishing, I don't even know what you would be arguing any more? "All things equal, you can earn more money from X." Yeah, okay, but they AREN'T equal so that study is of no value to anybody.