Originally Posted by docbert

Unlike many other airports around the world, places selling SIM cards at US airports are not common. Some airport do have them, either via resellers or kiosks/vending machines, but even when they do exist they are generally relatively expensive. Doing something in advance is always a good option. (I can't speak for Vegas specifically - I'm normally in enough of a rush to get out of the airport zoo there that I've never even bothered looking to see what they have!)