The fee you charge should always be relative to the current demand in the marketplace for your services. If you have no clients, than charging say $70-100/session probably isn’t wise, even if you are in a market than can afford to do so. That is, why not make your price an attraction as opposed to an obstacle if you are attempting to build a client base? On the flip side, if demand is high (or if demand gets high once you have your clients) than it is logical to charge a premium price for your services, assuming your services warrant such a price. Of course, as others have said the demographic of your target market must always be taken into consideration as well.
Simple stuff, nothing fancy. At least that is how I approach it. Good luck!