When I was overweight, I ate mostly cheap chicken nuggets (£1 a bag) and Iceland cheesy garlic bread (also £1). I was spending around £4 a day/£120 a month on food. Mounjaro starts at around the same price and only goes up afterwards, so even if I ate literally nothing all month, it still would not save me money.
I'm not sure why everyone thinks you need to spend loads on takeaways or chocolate and crisps to be overweight. I don't even like takeout food or most snacks.
OP, I'm not sure I can give you advice as I've struggled with ED most of my life and tend to eat everything or nothing at all but some things that do help when I'm restricting is having a small handfull of quick, cheap meals I can rotate daily that fit with my calorie allowance so I can stick to it without thinking too much.
Count and track every calorie. It is much easier to resist that Mars bar when you realise they are 228 calories, or the same as a portion of grapes, 1 large caramel snack a Jack and a curly wurly.
Volume eating helps if you are used to large meals, fill your plate with loads of low-cal green veg or salad. I bypass the potatoes and have extra broccoli instead. Protein is filling, so have some high-protein low-cal snacks to fill the gap if you feel peckish (boiled eggs, low-sugar protein bars, Skyr, cottage cheese with cucumber slices).
If you really, really, really need some Gregg's brownies with caramel dip, then tell yourself you can have them, but tomorrow. The next day, you probably won't want them as much, and if you still do eat them, but eat well the rest of the day. Constantly depriving yourself will only make you want junk more. Schedule monthly days off or "fuck it days" where you eat what you want, when you want, fuck the calories.