The Y axis is throwing me off a bit. If the X axis already shows the amount of protein per mass, why would you also couple the Y axis to the amount of protein? So all the products low on the X axis automatically increase along the Y axis. For example, the vegetables are probably that costly in this graph because they have a low protein content, not because they are necessarily that expensive.
Fair point, I guess this would be a good reason to plot it like this. Maybe the author of the graph should have labeled it accordingly to avoid confusion though…