More often than not: $0. :D I mean they are supposed to pay me in the $200-1600 range, but actually getting clients to fork up money for a completed job is difficult, to the point where I'm ready to give up and get a regular job.
I don't generally do jobs for less than $200 though. It takes times to do research, switch environmental and your head around, but clients sometimes think I'm a typist and should only be paid for time on the keyboard.
You really need a better class of client. A couple of things that I have learned: 1) you are more likely to get paid by big companies because the person writing the cheque isn't spending their own money, 2) you are more likely to get paid by people you meet face-to-face because its easier to be an asshole over the internet, 3) bizarrely you are more likely to get paid if you charge more because it weeds out all the penny pinchers. The last one is really important. Just by charging more you put yourself in a different market, one which is generally more professional.
I don't generally do jobs for less than $200 though. It takes times to do research, switch environmental and your head around, but clients sometimes think I'm a typist and should only be paid for time on the keyboard.