6,000 Lbs Food Grown on 1/10 Acre in the Suburbs

NY Times Mag reports:

Jules Dervaes and three of his adult children live on one-fifth of an acre in Pasadena, Calif., a block away from a multilane highway. On this tiny sliver of land, they manage to be mostly self-sufficient. “This is our form of protest,” says Dervaes, who is 60, “and this is our form of survival.” The family harvests 6,000 pounds and more than 350 separate varieties of fruits, vegetables and edible flowers annually. They brew the biodiesel fuel that powers the family car.

Amazing that they could grow that much food on 1/10 an acre in the middle of the suburbs. More information on the numbers and how they do it here. In 2008 they harvested 5,500 lbs and they have a goal to grow 10,000 lbs.

I am curious though how many calories are in the foods that they grew. They state that this accounted for 2/3 of the food eaten by 4 adults, which I would interpret to mean that it is enough food to feed 2.6 people, or that a 40' by 40' section of land could support one person. I am also curious how much they are able to sell this food for to the local restaurants and how many hours of work it takes to raise it. Would it make economic sense for more fruits and vegetables to be raised in suburbs, right next to their customers?

Update: Video here.