The Las Vegas Monorail has started a Cyber Sale good through December 5, 2013 at 11:59 p.m.
Buy One Unlimited 24-Hour Pass-Get One Free (2 purchased, 2 Free) Maximum discount of $24. Tickets purchased are good for 1 year from date of purchase. They say these cannot be redeemed between Dec 27, 2013 - January 2, 2014.
Enter the total quantity tickets you want and in the "Enter a Promo-Code" box enter code: cybersale13 .
If attempting to buy more than 4 passes then I would attempt multiple orders, not sure how they are controlling the purchase limit (by card or by address?).
For anyone in Vegas already, you can go to an Eticket kiosk at any station and use the same code to purchase and print (details at the same link). If you want to use cash you should be able to claim this offer at their customer service booths. I would advise printing the offer page if you attempt to use the booths.