In my experience open access still includes a big publisher sucking up tons of money. It is just money paid up front by authors. Do you have an example of open access were that is not the case?
Some disciplines have started moving to Arxiv. And all the major programming languages conferences (PLDI, POPL, ICFP, more) switched to PACMPL, which is open acess and I expect is cheaper but am not sure how to check. I don't know much about this; mostly just wanted to make the point that peer review != publishing.