No, you have it the wrong way around. The girls would love to get paid more but the studios aren't going to offer them more money when they can just fake it and still get the sales.
It depends on the girl, some of them charge less for real nakadashi, some of them even like it. On the other hand they probably aren't all that keen on taking the medication (the pill isn't common in Japan) and all the rest of it just to make the 397th identical video in the "guys discovers his neighbour works at a soapland" series.
For some of them it's also about maintaining their "pure" image for the fans. When an actress does one nakadashi movie right before retiring it's usually because she thought her fans liked her innocent image but figured she might as well make a few bucks off the ones who had been waiting for it, since her career is over anyway. In that case it's almost always fake.
I guess I'm dumb, I'll probably never get it.
To me it doesn't make sense that girls after quick cash aren't getting paid enough for having fake pen, but still signed the contract, just tell the agent who got you in to get you a better contract in another studio, the agent wants a bigger cut too, no?
As for those actresses who like nakadashi...(i don't really believe this unless they are fugly chicks) if they like it, why would they ask the studios for more $? Wouldn't the studios tell them: "hey, you get a nice creampie, you feel good, so the pay is going to be lower."
Idk what pure image they are preserving when these fake pens we're talking about were filmed like 2 decades ago and they were all censored back then, nobody knew it was fake. Also, maybe it's just me, but none of them are pure once they step into the industry. Sure, some girls appear to have a "purer" voice, personality, or behavior, but they don't lose it just because of nakadashi, for me at least, the turning point is when they start doing pee drinking or scat kink stuff; that's just way too much.