275 OW with 7 day advance? On Orbitz you can get a return LAX-LAS on HP or UA for $158 with a Fri/Sun departure/return which is the busiest/costliest combination. This is for next weekend 2/24 to 2/26.

Between America West, Southwest and Ted there are probably about 60 daily flights from SoCal (LAX, SNA, BUR, ONT) to LAS plus a handful of American Eagle and one or two JetBlue flights from. There is no shortage of flight availability.