Actually, you forgot the price portion of their question. He would need 11,257 mithril bars, which would cost 12,630,354 at medium price. It would make 112,570 mithril bolt tips, which would then need feathers costing another 675,420. This comes out to be ~13.4m. They would earn back 9,118,170 gp, which makes him lose ~3.8M. Although it would be faster, they lose quite a bit more. EDIT: Yes, but that would require a full team of people working to keep the furnace going for a while, since they're trying to get 55-70 smithing... I guess it's plausible, but since I've never been there, I can't really give advice on this. who said anything about making them bolts, no feathers! they sell at the moment you put them on the ge and there is almost no loss.