We spend about £450+ on groceries. Three weeks out of the month, the delivery is about £100, and one week it's about £150 as we have additional supplies (sanitary products, vitamins, cleaning supplies).
My children have SNs, and both have specific food issues so will not eat certain foods. They also need gluten free foods (as do I), so that gets more expensive too.
Because of their food issues, our diet can be somewhat boring as well, because I have to stick to stuff they will eat, although over the years, I've managed to slowly increase the variety.
No soups (except tomato), no sauces (except spag bol), very few "mixed foods." We bake our own bread (GF), bake cookies/cakes as needed with GF flour, and use UHT milk (because running out of milk or running out to the shops to get milk at the last minute is not something that can always be done in our situation - this means we always have milk on hand - and we all are happy to drink it). We have an occasional takeaway or meal out (like Pizza Express as they do gluten free). I try to avoid chicken nuggets, fish fingers, etc, simply because the GF options are pricey and it irritates me to pay that much.
Because new foods can be hit or miss for quite some time, we do have a fair amount of food wastage, but that's life unfortunately. It's important for them to try new foods.