m0loch,
I don't know if this is of use to you but Scenic Airlines offer staff standby rates on their tours from Las Vegas ( I paid USD 60 a couple of years ago ). You get a flight from the North Vegas airport to Flagstaff ( over the western end of the Canyon, but not into it ), lunch on arrival in Flagstaff and then a Coach trip to the Grand Canyon with about 4 hours there to investigate. On the day I went we had about an hour delay on the flights which meant flying back to Vegas at dusk which gave great views of the strip from the air.
Contact Scenic at info@scenic.com to get current rates.