LAS VEGAS—A trip to this desert city once meant dirt-cheap hotel rooms and buffets, all subsidized by gambling revenue. Now visitors organize their trips around big-ticket events—and pay top dollar for everything else while they are in town. Postpandemic Las Vegas is built to cater to the well-off. Hotel rates have risen faster than in any other major market in the U.S. New venues are drawing visitors to town for pro football, concerts and Formula One racing. A $26 bottle of water went viral last year. Not long ago, lower- and middle-income families and young partyers on tight budgets made…