Now now, let's not assume too much. Unlike crime drama or action thrillers, sexual intercourse is a low cost ($1 for a condom) low risk (no broken nose or cuts) activity. It's fairly reasonable for two (or more) to engage in sex for real, film it and put it out as a DVD. It's not very well filmed, but it's a viable business model. For top production, you want to adjust camera angle a few times, change sex positions, lighting, touch up for make-up. etc etc. So for high production value, the performers aren't able to enjoy the sex. But if you throw all that away and tell them just have fun and let the camera guy will do the best he can. Well that's another choice and certainly there's a market for it.Anything you see in a video is "made for the video". So the girl is acting, even in those amateur looking movies. They think about what their audience want to see. If the girl doesn't say anything during 60min, nobody would buy it.
For BLOR-175 I can give it benefit of doubt. In fact for most amateur looking/low production films, it's possible either or both players are enjoying pleasure during the filming. IMHO, porn should convey pleasure, which can be done with or without real pleasure. Yes it's true the majority of well-produced films look very "business-like". E.g. S1 Studio, esp. their top star Yua Mikami, I doubt she has ever once enjoyed sex. But on the balance of all factors, I still lean a bit towards top studios productions. Sometimes even top studios made me believe in the pleasure. I want to watch porn that looks good, not caring too much if any component of the production is fake, behind the scene.