I’d be surprised if that was actually true. I think what really matters is how much time and effort making your own food takes vs the speed and simplicity of buying fast food.
Price, time and effort can be minimized by making a large amount of the food in one guy that you eat for some days, but apparently some people hate eating the same food two (or more) days in a row, which, okay(?), I guess that’s one reason not to do it.