Aside from the optimizing-where-to-buy part, this sounds like what https://mealime.com https://mealime.com is attempting to do. I've only used it for one meal s

Aside from the optimizing-where-to-buy part, this sounds like what https://mealime.com https://mealime.com is attempting to do. I've only used it for one meal so far so but if you select multiple meals it creates a combined shopping list.