One site you may want to check out... http://www.summitgunbroker.com/index.html
I bought a used 4566 from Mark sometime ago, very nice pistol..think I paid $350 or so...he gets in all different sorts of police trade-ins...just have to hit it right.
We sell 4506 from 450.00 and up.The third gen. guns will soon be gone. S&W is trading M&P pistols for third gen guns,even trade. Soon there will all be gone.We have 4506, 5906 and 4566 in stock. But going fast!