Food and water can be quite cheap: the grocery stores are filled with healthy foods you can get for less than 1$ per lb in most of the US: corn, whole wheat flour, bananas, apples, grapes, onions, beans, rolled oats, etc.
The biggest problem with living cheaply is Housing, Healthcare and Tax. for the most part these are mandated by the gov regulations to be really expensive. Once those are solved, we'll be able to live quite cost effectively. I've seen some people get around that by living in a camper van, traveling the world - not for everyone, i know. But, the tiny house movement shows us we can get a tiny house for just 20K.