More on the unaffordability of healthy food

The data illustrated in this diagram dug up by Matthew Yglesias may have something to do with the relative affordability of healthy vs. unhealthy eating.I should note, though, that I think whoever put together the pyramid on the left was being a bit imprecise and misleading with its composition. It looks like the percentages were divvied up just according to length along one of the edges of the pyramid. But the relative values are perceived as being volumes. The ratio of the volumes of the Meat/Dairy portion of the pyramid to the grains part is not, I believe, 73.80 to 13.23. The point of the diagram stands, but the graphic representation exaggerates things.