I do think often the online posters talking of feeding a family for less than 50 week are not talking of full days worth of meals. Even above other posters have said things like lunch is just sandwich or salad, but in my house sandwiches for 4, five days a week cost a fair amount , with cooked meats -even using left overs means buying a bigger chicken, or ham, or beef joint, tins of tuna, cheese, pickle, tomatoes, lettuce, eggs, cucumber, humus, mayo, tins of beans etc etc all going into the shopping. And that's before all the bread, pittas, wraps, crackers. I do buy a lot of these and freeze as I find kids have a habit of not wanting same thing two days in a row ,and shelf life is short. Plus we eat a lot of things like toasted pittas as a snack. Again I generally will buy the supermarket own brands as a lot cheaper. Also buy supermarket brand butter, honey and jam.
But if I gave the kids only a sandwich for lunch, they would be hungry again so usually there is yogurts, fruit, left over pasta, popcorn.
Breakfast I don't find so expensive as I always buy big boxes of own brand cereals, basic ones like tesco substitute Weetabix, shreddies, cornflakes, porridge during winter , and loaves of bread for toast and jam , they consider peanut butter on bagel with chopped banana for breakfast as a treat. Also make pancakes a fair bit at weekends, and will freeze a few extras- again for those mid afternoon snacks. My older dd not so good at eating in mornings so she's more likely to bring something with her when she leaves house, like yogurt and fruit. I make her a lot of smoothies using fruit from freezer. My dh will have eggs everyday for breakfast, but then eats less for lunch.
I don't buy a lot of juice more inclined to buy whatever fruit is on offer, but aside from that we'd usually have apples, bananas, pears - the kid sized ones in packs are often far cheaper just have two , I'd rather we have cereal, yogurt or toast with fruit for breakfast than a glass of juice. Its easier to do portion control, my 12 year old could drink a carton of juice on his own in a day if let loose.
I find to keep dinner costs down the freezer really is my best friend, I use a lot of Tesco brand frozen veg and find its far cheaper than fresh, and great in a hurry in the evenings, like last night I used their frozen stir fry veg to add to rice and chicken. I always look at what's included in the meat/fish offers then build a meal plan around that. Trying to have at least 2-3 meat free meals a week as well . We have one vegetarian so keep en eye out for veggie offers too. I will buy the bigger packs of meats and will batch cook at weekend and freeze - I usually have a two week meal plan rather than one, so I cut down on the cooking time during week, but less boring that eating same meals every week, as nothing worse than getting in from work late and having to face into prepping dinner. While I do this to save time, I do find the cost of our dinners has gone down.
Unlike op I'm lucky to have an aldi and lidl near me at work, so I do check what's on offer and will often pop in and arrive home with extras that go straight into freezer for next weeks meal plan. I find they also same me a fortune on the random stuff like tin foil, tea , coffee ,laundry products.
I used to do a lot of baking but when I looked at cost really it was costing far more than it costs to buy a few treats. I still do it because we all like it, and I like knowing what goes into our treats, but I don't kid myself its saving money.