First research what your competitors charge. But you do not necessarily need to charge less. Sometimes charging a higher price creates in the mind of the customer a perception of higher quality, especially if the remainder of the presentation is consistent with high quality. You may need to do trials of various price points to see what works. These can be limited in nature and focused on particular audiences, without tipping off your entire customer base.
Some sites use auctions to allow the customers to set the prices.
Different customers have different perceived values for the services. No use setting a low price while there are some who would be willing to pay more, based upon their circumstances. One strategy that may work for your business it to offer specials at very low prices. Instead of paying gobs of money on promotion, you may be able to convert prospects who are on the edge, but not quite yet ready to buy on the internet, into customers. If you can nudge them into ordering from you, they may make online buying a part of their regular routine.