Apr 1 2012: Drones start from an AR.Drone (http://ardrone.parrot.com/parrot-ar-drone/usa), the one used for mapping is probably one from AscTec (http://www.asctec.de/?locale=en_US).
So: several hundred to several thousand Dollars. (Even cheaper if you buy a kit and do the soldering)
Apr 1 2012: It would be possible, but your velocity would be very limited and you would have to replace your quadcopter (at least its battery) every 10 minutes...
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A reply on Talk: Vijay Kumar: Robots that fly ... and cooperate
A reply on Talk: Vijay Kumar: Robots that fly ... and cooperate
So: several hundred to several thousand Dollars. (Even cheaper if you buy a kit and do the soldering)
A reply on Talk: Vijay Kumar: Robots that fly ... and cooperate