Honestly, its really not much from what I know.
Theres a taiwanese guy breaking down the JAV industry now. Just Youtube: 【市場觀察】少子化40年 日本AV女優為何越來越多?通縮經濟如何影響黑色產業?
Its all in Chinese though. some main pointers he observed are;
1. A recent law push for JAV girls to get paid per movie, I think...