The average MLS team is now worth $313 million, up an amazing 30% from last year. That year-over-year growth far outpaces the rising team values in the NBA (13%), the NFL (11%), MLB (8%) and the NHL (6%). And while such gains have come at a tremendous cost relative to those competitors—17 MLS clubs lost money last season, to just 10 such teams across the four other leagues combined—it’s clearly done nothing to slow...