I think a far better idea than cold calling companies or asking for price ranges on a message board would be to get a job in the industry. Not only will this give you an idea of how to structure your fee's it will offer (if you take advantage of it) a proper business mindset and insight into the other side of penetration testing.
Just having a certification does not necessarily mean you can go off and start pen testing companies. There are many elements to going off on your own, business development/operation is a quintessential skill. How do you plan on obtaining customers? Do you know people, or do you plan on cold calling? If you plan on cold calling your failure rate will be relatively high, especially if your name is not known. This is where getting a job in the industry and taking advantage of the contacts you make over a year or so comes into play. Aside from that, what Chrisg might charge will be different from what I charge, or what Kev or Don charges. Everyone has a different set of skills and experience that warrants a higher rate. I can tell you how much I charge but it does not do you any good. I'm not a CEH and most likely never will be. I have a single certification, but I've got degrees to include a masters in Information Assurance. On top of that I have years of experience in doing this, tried and true methodologies and a nice sheet of people who have given me quotes saying "He's awesome, hire him!" All of these elements allow me to charge more for what I do.