Another take on the cost of healthy food.
Firstly a basic assumption - healthy foods tend to be purchased as unprocessed (fresh?) single ingredients - beef, chicken, fish, vegetables, fruit etc. Only main exception is likely to be bread.
By comparison most unhealthy food is processed - numerous ingredients including sugar, fats, additives. Typical examples are pies, cook chill and frozen ready meals, takeaways, cakes, biscuits etc. High sugar, salt and fat content to "enhance" flavour.
Many years ago I read that to make a car by purchasing individual components would cost 10 times the price of the showroom model. There is a connection with food here!
In selling individual ingredients, major supermarkets make a significant margin on the price they pay the farmer/importer. This is to cover their overhead costs, staffing, store sites, checkout operators, IT systems, marketing departments, profit etc etc. They also want food which matches very precise specifications in terms of size, weight, appearance etc - particularly things like fruit and vegetables.
But a processed food supplier buys the ingredients by the ton, not the kilo (as the consumers). They are unconcerned by appearance and size which reduces wastage and purchase costs - eg: fruit that falls outside the supermarket criteria are almost valueless. Recipes minimise the use of expensive ingredients and are replaced by "fillers". Typically production processes are highly industrialised. Finally producers are hammered by the supermarkets on selling price.
It is no real surprise, therefore, that the price of processed food is so low compared to the alternative cost of the individual raw ingredients to prepare at home.