Yeah that is a risk, the general term is ROB, rip off bitch.
In my experiences I have always gotten what I paid for. There never was any question or any attempt at trickery.
It really helps to look at reviews and become familiar with the lingo. I strongly advice against turning to craigslist.
Another thing to look at are swinger parties. Usually it's much cheaper than an escort and you aren't limited by time, since most escorts want you gone by the hour. In the last swinger party I went to, I got to have sex with three women for only $50. All were in their 40's, two were average for women of that age and one was very hot. Be wary of groups that charge very high fees and require memberships. Those are BS.