The topic of food is a great one, especially when it comes to casual or low budget meals for more casual hikes.
When it comes to serious hikes, I already shilled for "Gear Skeptic" in the OP.
That guy made one of the best on trail nutrition guides I've read and worked with.

Bread is indeed a cheap, versatile pick.
As a central european I highly enjoy traditional "pumpernickel" wich is black, dense, squareshaped rye bread that won't spoil for a whole year when kept in it's foil-packaging and usually sells for 2€ per Kilogramm.
Swedish crispbread is also a peak hiking food for poor people.

For like 10€ you can get a small 3-tealight raclette-set so you'll have the option to have a nice slice of bread with melted cheese on top for example, any time, anywhere.

Or you can go all out and get a gas cooking setup, wich opens up a ton of options. I usually go for making mulled wine on casual winter hikes, reheating leftover stew, boiling dumplings or even fodue if I'm feeling fancy.

Baking calorie dense oatmeal-cookies for example, as well as doing your own trail-mix is also a good way to safe a lot of money with little time investment.

Oh and all kinds of dried meats and fish are also worth looking into...