I'm filthy rich these days so I don't have struggle meals anymore BUT back when I was dirt poor...
I was super in debt, barely keeping up on rent, and had to really cut my budget because my roommate and I couldn't afford our oil bill that came... and I bought 20 cans of "ValuTime Chili" which was something like 0.10/can on discount at the discount super market if you bought 10 of them. It was fucking disgusting but I basically lived off of that for close to a month. THat's when I realized I needed to move home because it was no way to live.
But then I figured out some pretty good meals. Rice, beans, and a hot dog (w/ mustard) is a meal that will keep you going and costs so little for each meal. 1 cup of rice, half a can of beans, hot dog + bun (or no bun if it's a tight week), and mustard stays good for a really long time and it's not expensive. THis was my go to for a while and I loved it.
I'd also do buffalo chicken quesadillas. Take a normal flour tortilla, which is cheap (20 of them for a couple bucks maybe), and then the Tyson chicken patties which I Don't remember the price but they were cheap, you'd get 20 for $5 or somewhere around there. I'd use usually Ken's buffalo sauce because it went a long way with just a little (much further than frank's or the Spanish one), and then just a discount bag of mexican mixed cheese (probably cheddar + jack). This was more expensive than the rice & beans, but it wasn't an expensive meal, probably a little over a dollar or so to put each meal together and they tasted damn good. The buffalo sauce and the cheese were the only expensive parts, but again Ken's buffalo was like $3 for a salad dressing container of it and it went along way, weeks or months. The cheese would be the most expensive part, but you've gotta live a little.
I honestly kinda miss those meals... My wife doesn't let us eat hot dogs with any regularlity and she'd make some gross face if I went to make my buff chick quesadillas... but they were fucking good and cheap. SHe's so judgememental of all of the food that I make and will always come up with a reason for why she doesn't want to eat it, even when I make a pretty good meal, and then we'll go back to fucking cauliflower no-dairy pizza or something and it's like... ugh... there's no joy in this food and it's way more expensive than it should be for fucking cauliflower.
(btw, I'm not filthy rich)