one of biggest costs is regulations, medical devices which this would fall under are are heavily regulated industry. The liability bill is enormous, let alone the costs of technology behind it.

anecdotal, a friend with an artificial leg needs it replaced every few years because of wear and tear on it and him. The fitting, maintenance, as well as physical rehab, is an ongoing costs. Hands don't experience the wear and tear that legs would so I wonder how 3d printed legs would hold up?