I make my own bread - not sure how much that costs tbh but bread is not massively expensive- less than £2 a week
They get 1 biscuit from a packet unless I'm organised and make some. A branded packet of biscuits is less than £1 and I use less than a packet a week.
sandwich fillings would be maybe 1-2 chicken breasts, 2 eggs, £1 worth of cheese, bit of jam or choc spread on fridays so maybe £4 for sandwich fillings.
I cucumber, a carrot, grapes, bunch bananas, bags oranges/apples/pears. They get 3 things, 3 dcs so 45 items a week. Grapes are the most expensive, about £2.50 a week. I got a pineapple last week for £1 and it lasted 2 days. They can have melon every day for £2.50 a week, carrots are almost free, you can get bags of mixed pepper pretty cheap and use the rest in other meals. Fruit is the most expensive part, maybe £8 a week.
They drink tap water.
Sometimes I'll make a jelly or split a big pot of yoghurt. (1 big pot does 2 days)
So even with melon, pineapple and grapes it comes to £15ish a week. School dinners are £36. (for 3 dcs)
Pasta is cheap, as are flasks of baked beans with cheese and bread, flasks of soup.