Oh goody, another post trying to 'prove' that it's not worth making any foodstuff yourself because it's more expensive than value level supermarket products that are not comparable quality wise.
I made apple sauce with some apples I picked up from a 'we have more apples than we know what to do with, please take some' bucket I picked up while out on a walk locally.
It cost:
apples (free)
sugar (pennies, a couple of spoonfuls from a bag that costs about a pound)
splash of lemon juice from the 50 p bottle that lives in the fridge, so again, pennies.
A few minutes electricity to run the microwave (not that much really, say £1 but probably nowhere near that amount).
It is currently stored in a mix of tubs, jars and bags in the fridge and freezer, all of which which were free/very cheap as mostly old jam/sauce jars or or takeaway containers.
Leaving aside the minority of people in temporary or very small accommodation because, despite what MN would have you believe, the majority of people do have at least basic functional and equipped kitchen facilities, it only costs 'a lot' to cook most things if you cost in every last thing you could possibly buy as if you're only using it for that recipe, instead of using thousands of times over decades, so the cost per use is too small to measure