Sustainable food

I find it provoking that some high end restaurants make claims to "sustainability" of the food they serve. To quote one chef: "The area around San Francisco has some very interesting local produce and has paved the way for local, seasonal and sustainable food in the past twenty-five years." 

And I wonder if I'm just being churlish. The prices don't make eating at say Rockpool a sustainable exercise for most people, and I recall they had quite a spiel on sustainable foodstuffs. Local food is nice and saves some transport energy but a huge investment of time and energy in a small amount of high priced may be straining the notion of sustainable.