500,000 swedish berry penny candies.
They're 12.72 calories each, which means you would need to eat 157 to meet a 2000 cal/day daily caloric requirement. That works out to 8.72 years of food. They seem to store reasonably well, so this is an added bonus for you preppers out there.
Might want to add a multi-vitamin to the mix for peace of mind which will increase costs somewhat, but that's still reasonably efficient. Not to mention the add-on bonus of not having to waste time cooking or figuring out what you're going to eat for eight years!
TLDR - Take your life back from the oppressive consumerist supermarkets . . . eat only penny candy.