3D-printed robotic arm for six-year old: $350. The ability to hug mom: priceless. Alex Pring was born missing his right arm from just above the elbow. The cost of a traditional robotic limb, which would have to be replaced as Alex grows, has a hefty price tag. But now, thanks to Albert Manero and his team of aerospace engineering students, Alex can ride a bicycle with both hands — for about the cost of a bicycle. The device is made with a 3-D printer and parts available in hobby stores.