Update (Sept. 7, 3:15 p.m. PT): Southwest Airlines Vacations' booking engine is currently pulling up higher rates for Circus Circus. To get the $99-per-person deal, find "Circus Circus" in the search results and under that, click on "Upgrade Room." Then select "Skyrise Tower room." Additionally, Denver's fare has increased to +$84 per person.
For $99 per person, including airfare, paint the town red in Las Vegas for three nights. Based on current hotel and airfare pricing, this makes the entire hotel stay free.
Pricing per person (based on double occupancy) from Los Angeles or San Diego:
Other departure cities from across the U.S. are also on sale. The best pricing is found for Sunday-Tuesday departures over the dates listed above:
Travelzoo Tip: Southwest allows guests to check up to two free bags per person -- a potential savings of $120 per person roundtrip compared with other airlines.