Maybe the average key milling machine can't do it, but a general-purpose mill could. And for less than the cost of a 3D printer that can make strong finely deta

Maybe the average key milling machine can't do it, but a general-purpose mill could. And for less than the cost of a 3D printer that can make strong finely detailed parts, you could buy a decent sized CNC machining center that could make keys (or anything else) out of real actual metal. For a tenth of the cost (or about the cost of a hobby printer), you can get a manual machine and do it by hand.