Notes
It actually proved rather difficult to find the present cost of the mule trips. However, according to http://www.grandcanyonpark.info, which does not appear to be affiliated with the park, the 2011 cost of the overnight trip "is $477.34 for the first person and $842.60 for two people. This price includes accommodations, breakfast, lunch, and steak dinner. The price for each additional person is $378.08." The one-day trip is no longer offered, having been replaced with a 3-hour ride that merely gets you out to a point where you can look into the canyon. Again, http://www.grandcanyonpark.info reports that the 2011 cost of this "mule ride is $117.40 per person, including tax."