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http://www.armygear.net/ag/store/00231.html

TWO CASES of MRE's for a total of 24 meals, for $89.98 (about $30 for shipping).

Unless you're doing some really strenuous physical activity, you DON'T need to eat 3 of these a day. (Each meal contains around 1200 calories.) So this would last longer than you might think.