If porn is free on the Internet, then how do porn stars actually make money?
Using Google is also free, yet the firm is quite profitable, so a possible solution could be ad revenue.

Another solution could be that your sampling is off. E.g. most urban Democrats do not know many rural Republicans and vice-versa. It is similarly possible that people who do pay for porn do not move in your social circle.

There is also an incentive issue to your sampling. This is a subject most people probably do not wish to discuss. As such you can reasonably doubt if you are getting honest answers. If one were to answer your question in the affirmitive, he would incur not only the stigma of watching porn, but also the stigma of having paid for it, which as you say is kind of strange given its free availability.