Unless you are rich I see no reason to buy over-priced MRE's!
Hardtack was the traditional staple for military use. You can make a better substitute with high-protein flour, dry milk, salt (or use potassium containing Lite-Salt) sugar, canola oil, oatmeal, etc.and water. Roll the dough out to about 3/8 thickness, cut with a cookie cutter and bake very well at 400F to drive off the water. store air tight. You need about 2000 Calories and 60 grams protein, per person, per day. Do not forget to also store Vitamin tablets and extra vitamin C! The cost should be under one Dollar, per person, per day.