BFL, I respectfully disagree. Although the food is only worth $20 retail, its value to an off-grid camping trip is priceless -- if the food spoils, you have to go home or go to town to get groceries. How much is it worth to avoid wasting a day of vacation on a needless shopping trip?
Plus, the thousand dollar capital cost of the panels has to be spread out over many, many loads of groceries. If the food is worth $20, and you sink a thousand dollars into the panels, that works out to fifty nights' worth of groceries. We almost always camp 60 to 90 nights each year. So the cost of the panels is justified in just one year, and of course the panels last longer than a year.
Bottom line -- a properly-sized set of panels is a good investment.