While looking around for bulk apple juice pricing on the web, I came across an article: A new enzyme increases juice yields by 80-90%. Wow.
New enzyme promises higher yields to apple juice processors
I remember reading that in the old days, they pulped the Apples and let them age for a little bit to soften, season, change the sugars, flavor, and consistency -- THEN they'd mash'em. It was supposed to increase the sugars in the pulp, and increase the juice from the pulp. I think I would try that, if ever got to the place where I would have batches of apples to process.