You would never imagine that a 3D printed hand costing about $50 in materials, would outdo a $42,000 myoelectric prosthetic, but that's just what appears to have happened. The Cyborg Beast 3D printed hand which I am sure you have all seen somewhere in the past, outperformed the device which costs as much as a new BMW.
http://3dprint.com/2438/50-prosthetic-3d-printed-hand/

3DUniverse provided a man named Jose Delgado Jr, with the open source 3d printed hand, and then had him use it for several weeks as he performed his labor intensive job. At the end of the period he told 3DUniverse that he preferred the $50 Cyborg Beast to the $42,000 prosthetic he had been using for over a year.