While I have never been employed as a programmer, I recently started doing freelance work. My reasoning was as follows:

• It is 2AM and my wife is annoyed I am still on the computer.
• Explanation 1: Someone posted a really interesting problem on PerlMonks.
• Explanation 2: Someone is willing to pay me what I would have done for free if they had posted to PerlMonks.

My rates are typically $35/hr for non-profit and $50/hr for corporate. I also offer flat fee rates per project which result in lower cost to the client but with the restriction that I work on my own time table. I typically don't take anything requiring more than 20 hours a week because I work full time. Everything is flexible for me because I don't need to do this.

I get a steady trickle of jobs despite not advertising. The clients don't complain about my rates and are happy enough to come back later.

Ok, so how does all this relate to your post? I would say that at least 60% of the jobs I get is to clean up after a $10/hr freelancer that made a mess and didn't finish the job.