Michael Pollan, the best-selling author of "The Omnivore's Dilemma" and a leading advocate of buying locally grown food, recently upset many of his fans by daring to put numbers on his oft-repeated prescription to "pay more, eat less." Eight dollars for a dozen eggs? $3.90 for a pound of peaches?

Those figures were way too specific and way, way too high to go unnoticed. The humanistic foe of industrialized eating suddenly sounded like a privileged elitist, and the local-food cause seemed...