Cost is very dependant on where you are, and the level of shop that does the work. As in most things, the cheaper the costs, generally, the lower the quality of work. What is fine for some applications, may hurt others. IMO, paying to top notch work is only a win win, as great machinjing can make cheaper parts perform better than expectations. That said, a basic rebuild, on average equipment, for average money, can make very good power so long as the pistons are replaced with something that give you more compression and performance valve reliefs to allow for performance cams and the camshaft chosen is matched well to the rest of the combo. You'll still end up spending close to $5KUS to reach a level of 400-450hp if you have nothing but a stock core engine to start with. But again, you might find your local shops are cheaper.