I thought of a couple more that I'd heard from clients.
1. One scam is the "Oh, gee, that $150 is just for me to show up at the door." And then the escort will itemize a list of sexual activities, so that the equivalent of a "girlfriend experience" will cost you as much as a Thai wife. I hear this trick is particularly common in Vegas, where they hand out flyers for $100 escorts. As they say, if it sounds too good to be true....
2. Another scam is usually done by a quasi-legal pimp agency, that'll sorta make it sound like they're sending an escort, but then when she shows up, By Golly, she can't do any of those things because they are illegal! She can only strip and you can service yourself. Unless of course, you're willing to pay her liek $1000 and then she's pretty much open to anything.
Both of these scams are definitely of the one-timing variety and are done by agencies or pimps, because most independents want to encourage repeat customers. That's my opinion of course.
Just more to think about before you make an appointment. Again, reviews are the way to avoid both of these.