The top sites above aren't doing badly, as English sites are dropping while other language sites keep rising up in world ranking.
CL Craig's List isn't primarily an escort advertising site, but it actually is. You can count the handful of posts in say jobs, and compare to the hundreds of posts per hour in the erotic service section. It's free.
TER The Erotic Review is an escort review site paid for by membership subscriptions. But for your own benefit, players and playmates alike, treat reviews as advertising and you can go no wrong. The traffic is probably more than all the other escort malls combined.
CV City Vibe learns from CL. In the beginning, if CV sees pretty pictures in CL, they will invite the author to advertising on CV classified. It's free for everybody but few read it. At first it seems contradicting, the free classified in CV competes with it's own paid advertising. But it's exactly like CL. CV hope to boost the traffic rank with the free advertising section. There's no way for outsiders to tell whether people read the paid advertising or read the classified. Without a boost, who would want to pay? CL is free and lots of readers. If you ask somebody to write a review for you in TER, it's much more effective. All you need is a free homepage somewhere.
TBD The big doggie is formally dead. So please don't bother about reviews there and don't post your touring dates there - nobody read it.
CL has big problems because they don't give a dam about the escorts section; they don't make money out of it. But they will do their best to keep up the traffic, without it they are nothing.
Personally I have simple software tools to deal with CL to make life easier. It's a sort of custom download accelerator so you don't have to click on the title of every post to see the content. I surf CL as well as other malls, but CL is just much more interesting. Calling someone up is a totally different matter.
Now some online newspaper are copying the CL model. They allow much higher resolution pictures. If you pay up, you can have bigger ads in better locations.
200 x 10 x 5 x 50 = half a million
That's the formula to make half a million in a year tax free, in 50 weeks, 5 days a week, 5 hours a day for $200 per 30 minutes.
It's not good nor bad. And of course it's not sustainable. But that's the idea, you can even make more. All the tools are available for you to do it compared to a couple of years ago, or may be just last year. You can spread the money over several years or more, but the risk is much greater.