It's not my area of research, I read things over the years and following the good advice of Sherlock Holmes: I force myself to forget useless details. So I could be wrong or inaccurate in the following:
Recent years DMM/Fanza release somewhat surprising data that women accounts for a surprising fraction of consumers of porn, something like over 30% (the conventional wisdom was women is less than 5%, more like 1% of the consumer base) and even more surprising is that top idols, the likes of Kirara Asuka are admired by some women who don't even watch porn. They know she's AV idol, they don't necessarily watch her porn, (esp. not masturbate to her porn) but they respect her feminine sex power and ability to charm men. So boom, her fashion (outer wear and underwear), lingerie, cosmetics become bankable merch. Even things that never appear in any AV, whatever she eat or drink (food supplements), personal care products, plastic surgery etc can all be marketable. I don't have any specific details, but Kirara Asuka has a reputation of only wearing and using expensive luxury brands, underwear, outer wear, hangbags, shoes, jewelry, everything on her person are not from average shopping malls. She's a curious case that her appearance in her JAV are perhaps less glamourous than her off-camera self. Her male fans don't care about these (not consciously) but there are female fans who wants to be her (at least the rich and luxury persona of her, not necessarily including the sex-for-money aspect)
Eimi Fukada, very famous for using a ton of plastic surgeries all over her body, become a spokesperson for a hostipal and gave very detailed explanation of some borderline grusome procedures that she had done and that her audience may consider to have done. The details even include for how many days and weeks after the procedure your face will look like a hockey player. It's highly adviced for male fans to avoid watching/reading these.
Yua Mikami: she has so much going on, it would be insult for me to just list a few. One example of her marketing powress is her own exclusive personal make-up artist is famous on social media, his handle is some like "Yua Mikami's make-up artist".
Like my wife said, we knuckle-dragging men don't even notice when women get hair-do or new cloths, but subconsciously we do notice and turn our head when a hottie walks by. We might not remember the color of the dress or length of her hair, but we turn our heads, and women would spend tons of money to be like the women who turn heads.
SOD is literally a business empire with porn being the center piece, but it's actually only a small centerpiece. They are a huge brand name for sex toys and related personal care products, more than I can give justise to here (because it's not something I care, i mean I consume a lot of porn and love sex with women, but other than generic brand lube I almost use zero products for sex). SOD also operate JAV cafe and similar services. No you will (almost) never meet a real JAV performers at these venues, but still there are enough customers to keep the businesses going. The rather large fuzuku (prositute) industry in Japan, I imagine, is a big customer base for SOD products, e.g. lingerie, fuzzy handcuffs etc.
