One point I didn't see mentioned in the article is that in the case of the Big Mac, it's likely that McDonalds sells the burger at a lower profit margin so that

One point I didn't see mentioned in the article is that in the case of the Big Mac, it's likely that McDonalds sells the burger at a lower profit margin so that they can sell more fries and drinks (the real moneymaker). I'd like to see the data, but I'd bet that 95% of Big Macs were sold as part of a combo that included fries and a drink, and 95% of salads were not. To my knowledge, salads are not included in any value meals at McDonalds. Couple this with the fact (mentioned in the article) that the ingredients in a Big Mac last longer in storage than those in salads.