Napa makes up 4% of California’s wine production, but its grapes command the highest prices. Over the past few decades, the median price of Napa grapes has surpassed the steady rise of other California regions. “In Napa, they are willing to pay an awful lot for cabernet,” says John Aguirre, president of the California Association of Winegrape Growers. As demand has exploded, so has the grape supply. In fact, there’s a surplus—so drink up.