A look at the examiners who chose to be SOT certifiied is an easy way to see what others are charging in your area.  The SOT certification requires posting your prices.
On another note, one thing that bothers me locally are examiners that charge a higher rate to the local clients, and give a discount to the national vendors for the same work.  I fail to see how helping the national vendors push down prices, and drive the local agencies out of business is good for the independent examiner.  As Shannon said, it is a question of ethics, and I just don't see any ethical reason to favor a national vendor over a local client.