Yeah, even though fast food is often looked down upon, it's actually a luxury food. I enjoy fast food about 3 times per week and it costs almost as much as all other groceries summed up. If i had to cut costs, this would be the first thing i'd cut. I would eat rice, legumes and tomato sauce instead (maybe with toppings like canned fish or tofu) would easily save me >50€ per week. You can buy cheap high quality rice in huge sacks (often with zippers on top) to save even more.