The bottom of the sleeve is has a different taper which I believe is done after machining but I am not positive. I know for sure that the crank has been modified after machining, you can see it when you compare a stock and MRT one. I would also think that they match up pistons and sleeves for the perfect fit. The mag head is something that also would be more expensive than the stock aluminum one. All of that takes some extra time and costs money. It is still a good deal I think.

Paul