For the most part, memberships / sales are stolen not through better marketing, but rather through deception and lies. More often than not, they are then sold a 30 day membership to another site.
The very basics of ANY retail business is to bring them in for what they want, and then sell them what you want to sell. Why do you think when you go to a supermarket or retail store that they crowd all kinds of things like gum, magazines, and other items near the check out area? While you are standing in line, you are more likely to consider and pick up what you didn't come for in the first place.
Many stores put items on sale at or below their cost. It would seem to be a dumb business move, except they are hoping to sell more than just that product on a visit. Example, computer stores selling printers cheap and then selling you a massively overpriced cable to connect it to your PC (and would you like an extended guarantee with that?).
The porn business again isn't any different from the real world. From batteries to potato chips, they are packaged in groups or by weight. Even if you need 1 battery or only want a handful of chips, you end up buying a pack of 4 batteries or a full bag of chips. We don't typically sell a single scene from a movie, but sell access to the whole movie or a site filled with similar videos. We package enough stuff together to justify a price of $29.95 a month (or whatever) to make the business model function. The costs of obtaining and selling a single scene to a customer is the same as selling the entire movie or site, so why would you want to sell less? The full site access (or in many cases the multisite access) is a way get a larger part of a customers porn budget to come to your site and make you money.
Pam, I understand where you are coming from, but you are also addressing a relative niche market that is use to having to work hard to find what they want. They are not faced with endless selection. Consider the amount of teen porn out there to the amount of true hairy porn out there. When you get into a narrow niche like that, if you can lasso enough traffic, you will always have a very profitable business because the surfers are all but pre-sold coming in the door.
(lucky girl!)