Know your competition really well.  When the client calls and wants it too cheaply be unafraid of referring them to the competition and telling them the competitions pricing.  Tell them exactly why you are doing so:  that you have no fear of the competition as you provide a superior quality product at higher cost and for the following reasons, 1,2,3...

They may use the competitor for a few cheap projects but will come to you when the realize the  lack of service speed, accuracy, quality, scope, coverage and knowledge.  Know the enemy, anticipate the enemy, beat them at their own game.... that's business for ya.