Of course this is comparing to one data point that is an outlier. If people are choosing to pay $3 in today's dollars for it, that means that in 2010 McDonald'

Of course this is comparing to one data point that is an outlier. If people are choosing to pay $3 in today's dollars for it, that means that in 2010 McDonald's was underpricing that item relative to its market value. Presumably deliberately as a promotion. Compare across everything you buy and compare like-to-like if you want to judge its accuracy.