"Strippers make more money than prostitutes"

Here's why:
In my area, a lap dance costs between $5 and $20. For the purposes of this example, we're going to say that $10 is the magic number, because that's what my friend made. Now, lap dances last the length of a song, about four minutes, and on a busy night a dancer can expect to be requested for ten or more dances an hour. To keep things fair, we'll average in the slow nights too, and call it 7 dances per hour. Typically the clubs around here close at one am to keep the cops happy, and shifts start at five, so the shift is 8 hours long. Let's do the math: $10 * 7 d/hr * 8 hr = $560, a pretty solid pile of Benjamins for eight hours work. We'll guess that the dancer decides to tip out 10% to the club's bouncers, leaving her with $560 - $56 = $504 on an average night. Nice.

Okay, the numbers are going to be a little sketchier for the out-call prostitute, since I've had to glean them from online references instead of a primary source. For my area, the running price for full service (which means exactly what it sounds like) is about $150. Now, I'm going to guess these ladies work reasonable seven or eight hour shifts, but need an hour or so of clean-up and travel time between clients. That gives us .5 clients per hour, or four clients per night, which seems like a nice brisk trade. Multiplied together, we get $150 * .5 cli/hr * 8 hr = $600. Of course, we can't neglect the escort service these girls work for, which probably lops a massive $50 right off the top of each client's payment. This step, finally, leaves us with the prostitute's earnings, $600 - $200 = $400 per night. Evidently even high class escort prostitutes make less than plain vanilla exotic dancers.

Just for fun, we'll compare these two salaries to what an inner-city street-walking prostitute might expect to make. I warn that this is almost completely conjecture, since the site referenced below had much, much more information about prices of escort style prostitutes than streetwalkers. We'll assume the average price for a half hour of "service" is $45, averaging between all the (ahem) kinds of service offered. Let's also assume an 8 hour shift, for convenience's sake. So, we've got $45 * 2 cli/hr * 8 hours = $720, which seems like quite a lot. Unfortunately, we've left the pimp out of the picture, which he wouldn't like one little bit! Once his 70% cut -- and that's a low estimate -- is figured in, it leaves the poor girl with a paltry $146 a night, by far the least of the lot.