Price structures are always tricky to come up with and they seem to change depending on the weather, the client and the mood of the investigtor.  I don't agree with it, but I've done it myself.  For sure, you'll need to understand what your operating costs are and make sure you cover those in any fee structure.  You might want to call around or ask other investigators what their rate structure is like and stick to something close.  Don't try and undercut the market, that never works.  It is fair however to price according to your costs.  For example, I don't have the marketing budget that the big nationals have, so I can charge less, because my overhead is less.  I don't want to charge too little, so maybe I keep it near the bottom of the “average” because I can.  It depends on the market you are in as well.  Insurance companies pretty much set the prices that they are willing to pay you, so there's not much you can do there.  Criminal defense is different.