I had my heads gone through this past summer. It was just a bit under $500, but I provided the new valve springs and the new valve seals to the machinist when I took the heads in. In addition to doing the inspection, cleaning and valve job, he also had to machine the surface of both heads. All of the guides on my heads were in good condition. If guides have to be replaced, that adds to the cost. And don't let them "knurl" the guides if they are sloppy. As I understand it, if a guide is bad, it must be machined "off" and a new guide press fit into the head.