My ultimate struggle meal:

In 1 pot:

• Rice (the good one from a sack, forget about minute rice)
• Carrots, sliced
• Whatever is cheapest between Sweet potato, Pumpkin or Eggplant at the time, cut into cubes.
• Thai Curry paste & Soy sauce
• Salt
• Cook 15 minutes
• Put into a tortilla with mayonnaise

Fast, really cheap, and has the important bonus that the only dish to clean is the 1 pot. When struggling, I also don't feel like doing a lot of housework.

Sadly, I can never remember the best ratios, so the mayonnaise is rather mandatory as it can save a rather bland filling. Sometimes, I splurge and use guacamole instead, sometimes I also put in mini-spring rolls from the same shop I buy the rice and curry.

With my "recipe" out of the way, the important thing is to find some ingredients that have a low price for lot's of weight, and then choose a recipe that's like 90% cheap ingredients by weight. (Remember that some ingredients take on a lot of water, rice taking on twice it's volume for example, so they're cheaper than the price tag implies). I personally look for food that's under 3€/kg. The other 10% of the meal can be way more expensive (curry paste in my recipe), but, because you only use so little of it, as a whole it's still cheap.

Probably the absolute cheapest meal are homemade hash browns, potatoes are ridiculously cheap, with apples being the cheapest fruit where I live. Next cheapest vegetable around here are carrots.