They don't really not pay the models. A good 95% of the 'reality porn' sites are actually staged...As in, they don't actually pick random people up off the street, or pretend to be cops to take advantage of totally unsuspecting people. You can normally tell, even without the dead giveaway that is 'amateur' model drift.

The reality is, the reality porn sites that are legitimately random and/or real...tend to get sued or indicted.