Meatloaf: In Germany we have a dish that is like very small patties out of ground beef, egg, old rolls (soaked in milk), onions, herbs etc. called Fleischpflanzerl https://www.chefkoch.de/rezepte/1537291259595500/Bayerische-Fleischpflanzerl.html
As I only buy organic ground meat (about 7 USD for 400 grams, mixed beef and pork) I stretch the loaves/patties even more. I add more bread (old bread that has gone stale) and cut oats, or I make them vegetarian altogether (based on bread or pulses like lentils). When they are condimented wisely, the kids will like them.
If you want to stretch ground beef, you can also use it in lasagna or bolognese style pasta sauce.
Another cheap dish is risotto where you can use a veggie like fennel or just onions and carrots.
My aunt gifted me a traditional Bavarian cookbook which is still very popular (many households have an edition) and it contains all the classical dishes that were used to feed the family without spending a lot. Traditional dishes include a wide variety of vegetarian dishes based on potatoes or eggs and flour ("Mehlspeisen", a tradition we share with the Austrian kitchen). Meat was mostly for sunday roast.
The book has all the basic classic recipes plus tips on frugal cooking (including offals).
Spätzle is a dish I often make, and I have taught my eldest daughter how to make delicious vegetarian gravy to go with it. It is also a big favourite in our family.
Tonight we had easy-style wraps: Just make pancake batter (luckily we have our own eggs), use a pancake maker in the middle of the table, and fill them with chili-sin-carne (I used kidney beans I soaked and cooked myself, a can of tomato sauce, onions, garlic, cumin, paprika, chili powder, fresh cilantro) and grated cheese. We had a bit of creamcheese left as well.
It was delicious, and I served it with a big bowl of salad from the garden (lettuce and all sorts of edible herbs and weeds and three mushrooms I harvested from our mushroom cultivation box).