It sounds like the control system is the expensive part. It uses a Vicon motion capture system to track the quadrotor using 20 cameras arranged around the room,

It sounds like the control system is the expensive part. It uses a Vicon motion capture system to track the quadrotor using 20 cameras arranged around the room, plus custom control software running on a laptop, and an XBee wireless link from the laptop to the quadrotor to send the control signals. The interesting part to me is the overshoot you see when the quadrotor shoots through the window, then pulls back nearer into a resting position. This implies that the control software can work out a dynamic trajectory (one where the quadrotor wouldn't be able to hover at every point along the trajectory), then reconcile it with a desired end point that won't fit onto the trajectory. That sounds simple, but many walking robots still can't do that -- their gaits are designed so they could freeze in place at any time and still not fall over.