I'm a big fan of soup and tuna melts, which are cheap and filling in the winter (though i guess you don't have it that cold where you are.) I don't know if they sell cheap rotesserie chickens down there, but I get a lot of mileage out of a chicken, which here runs about 7 bucks cooked (you can then scrape for chicken salad sandwiches or soup if you're talented). Baked potatoes in the UK style (by which I mean with fillings) are fun for kids: you can put them in the microwave to cook and then give kids shredded cheese, tuna and mayo, or sour cream, or sth to put in them. Pasta like someone else said and you can also throw, like, canned peas or beans over pasta with butter and maybe a little parm and that's a big meal and tasty and like four dollars.