How 20,000 pounds of anchovies spend 3 years transforming into expensive anchovy sauce

Colatura di alici, which is Italian for "anchovy drippings," is a traditional sauce produced by fermenting salted anchovies inside small chestnut barrels. It's prized for its umami flavor and very expensive, selling for $160 a liter. Here at Nettuno, the third-generation producer Giulio Giordano ages his anchovy sauce for three years to make sure it's the perfect color and flavor. But how exactly is this sauce made? And why is it so expensive?