Interesting thread, with many aspects. If I may comment on the original question, to me it's definitely about the storyline and fantasy element. I have joined paysites before when they triggered a special something for me. I am also seeing which sites convert the best for me.

I am talking straight sites here, but I imagine the same would be true for gay sites too. It is never an issue of lighting or setting, or how pretty the models were. I have seen sites that had the technical aspects polished up to the point of perfection. Point in case, sites like Hardcore Babes or Me and My Pussy by Platinum Bucks. They have absolutely gorgeous girls, very well shot porn, in terms of lighting, setting, shooting angles, you name it. You can see the movies were shot by pros. Then take a site like NetpondCash (now Cash Uncovered) with their Dogging site. Nothing wrong with the quality of the shooting there, it's perfect for the night time dogging atmosphere they want to create, but they also have that extra angle, that fantasy edge, that story telling of something wonderful and bizzare.