Wirelessly posted (BlackBerry8530/5.0.0.601 Profile/MIDP-2.1 Configuration/CLDC-1.1 VendorID/417)
If you'll be staying in or around downtown Washington and are willing to fly Economy, I would suggest looking into Southwest's flights from BWI to LAS. Southwest offers a few nonstops, and several other direct flights on this route, and offers free checked baggage. There is also convenient rail access to BWI from WAS Union Station.
If you catch one of Southwest's sales, you can probably find a one-way for around $150, depending on day of travel.