Why build robots with Lego NXT? In student labs at ESU we have used Lego RCX, Lego NXT, Boe-bots, and Vernier sensors. I also have several Roombas. Robots are expensive. Just the gripper for a typical industrial robot costs more than a new car. I also wanted to be able to try out many different robot designs. Lego is not cheap but it was the most economical of the choices we had.