I don't believe the cost is as high as you might expect. I have a friend who's building a full sized replica of the Jupiter, using the patterns owned by the US Park Service at Promentory. (yes, 12" to the foot scale.) The castings were pored this last winter and he's been fabricating other parts for almost a year now. He's going to have the boiler built by an outside firm. This guy is practical businessman and I know costs are being watched as he expects to be able to make a profit on this venture when he's done. One of the potential bidders for the boiler has expressed interest as they expect there will be a small market for replacement locomotive boilers for the museum & tourist RR crowd. Of course the boiler will be ASME certified & will meet all FRA regs for operation anywhere in the USA.