The machine work isn't all that expensive, I used to do one for $150.00, and like anything else, depends on how much ya want, and how much ya got, and how much you can do yourself, a guy on a budget with some mechanical experience, and a book on the engine, can probably build a good engine for under $3,000.00, but, there are a lot of parts still available, that can be had for a lot less, that's what separates the man and his money, when we were running Honda's, and running full seasons, I could get at least 3 seasons out of an engine, maybe a set of rings and touch up the valves during the winter, rest of it was good to go, a guy like me, with a lot of years in the mechanical and fabrication ends of racing, my costs were a way lot cheaper than the go-karts I had ran since 1958, but then, I was doing my own work on them also, as well as for others, I had as high as 5 guys working 5 nights a week on them! Bob