The prices charged for bicycle fittings will vary because of the experience level of the fitter, the depth of the fitting process, the amount of local competition and the local economy (wealthy neighborhood or not).  Find the most experienced fitter you can get to and set an appointment for your fitting.

Bicycle Fitters are just like every other profession – they fit into a nice Bell Curve.

Chart: imjustaguy.wordpress.com

You have a few really good fitters, lots of average fitters and a few lousy fitters. Find a Certified Fitter, preferably certified beyond the "basic level," and talk about your cycling comfort/performance concerns and listen closely to their answers. You’ll be able to tell if they know what they’re talking about and enjoy performing bicycle fittings. If you’re comfortable dealing with them, set an appointment for your fitting.

You’re not buying hamburger, so focusing on finding the lowest price can actually injure you if the fitting you get is done improperly or by a non-certified, inexperienced shop rat. Keep in mind that if you pedal at 85rpm, a typical 3 hour, 50 mile ride involves over 15,000 pedal strokes with each leg. And that’s just one bicycle ride. Over-use injuries are the bane of cyclists because of the repetitive motion. Your bicycle being out of adjustment just a bit can easily cause injury, especially in your knees and hips – and that’s not even mentioning the simply being comfortable part of riding.

If you’re the average recreational road rider (1500 miles), you spend 100+ hours each year on your bicycle. Spending $100-200 USD on making your bicycle comfortable and injury free for several years of riding seems money well spent.
                                                                                                          A poor bicycle fitting.