The problem here is the people think the M3 is some special rare car. We have KBB and NADA for a reason. Look it up and if the car is in excellent condition the offer that price or just under.
And for people selling a car those KBB and NADA values are where you should start. Why the hell would some one buy a car for way more than its worth. And please remember you DONT get the cost of modification back when you sell it.