It's all crap anyway. How can you eat that stuff? Maybe the value meal has more paper wrappers/boxes etc. My experience with food service is that the food cost less than the wrapper. I know that the plastic lids on the drinks are the most expensive part of the drink.
It is not the food that cuts the profit margin it is the advertisement and the wrappings, also the napkins, bags, condiments and straws. This is what you are paying for. So, if the same food comes in a different wrapper or box, you will pay a different price.
Mark up on the food can be 200+ percent.