Allow me to clarify a bit, because I used to be a serious fucking degenerate and so I know a bit about this topic.
There are three main types of porn sites: aggregators, pay sites, and cam sites.
Aggregators gather up free videos, but if you look at them, what they actually are in most cases are: old videos in full, small segments of new videos (which you either have to pay to get ahold of in full, or dig around on shifty websites that dump malware), amatuer shit uploaded by degenerates who've joined the aggregator's "community".
Their advertisers are likewise in three categories: clickbait dogshit that leads to more malware sites, or that lead to pay sites, or that lead to cam sites. Basically, the pornographers use these to lure you in - hey, free porn! - and for many, they can't resist the urge to click on the click-bait link (usually it has the most-degenerate or 'enticing' bit from a given scene in one of their videos, or some camwhore doing really degenerate shit, or just some nonsense like "Hey make your dick grow bigger!").
In short, aggregators are nothing but bait… Sort of. They're also basically pseudo-pimps via proxy, but I'll come back to that in a moment…
Then you've got the pay sites. These are where most of the money is made, and yes, while its insane to think that people pay for this shit (especially if, like myself, you learned how to avoid the malware on the malware sites so you don't HAVE to pay in order to see whatever you want), they do - most 'normies' don't realize you can get basically anything for free online so long as you're clever and know how to use the sites/avoid their malware, so they will be inclined to pay for access to a site that most channers would only need to even know about in order to effectively search for the video in question. As such, pay sites end up making a lot of money, and they tie into the aggregator bait, in that they post snippets of their videos on there (to entice) and/or post ads for their site on there, usually, as aforementioned, utilizing the most extreme/'enticing' part from a given scene or video as the ad, basically a gif on repeat (ie: the ad for BLACKED or the like will be a close-up of big black cocks slamming into white cunts, interspersed with images of beautiful girls rolling their eyes in pleasure or other such shit).
In any case, these sites DO make a lot of money, because A) normies are stupid, B) normies have no self control, and C) normies are the most likely to have disposable income AND have that income set up so they can quickly employ it online.
They also trick gullible normies, by having their adverts/sites imply that "Its just $1 a month!" or "Get a free 1 month trial!" or the like… What those normies don't see, generally, is that small print, which is that if you don't explicitly cancel your subscription - something that often requires more than just clicking around on a site, you'll actually have to call a telephone number and speak with a real person about why you need/want to cancel your subscription to BlackCumOnWhiteFaces.com or what have you - and alotta normies just wont do that. They'll just leave the subscription going, and accept the access to free porn coupled with a minor cost instead of the embarrassment and time wasted trying to cut ties to the pornographers.