Price ratio of leafy greens to starchy vegetables

In our house we disagree on the true nature of the potato.  I say it does not really count as a vegetable (like kale or green beans).  This map helps show why I think potatoes shouldn't be considered a true vegetable.  Dark brown areas are where green leafy vegetables cost $1.64-1.86 compared to $1.00 for starchy vegetables.  Notice that Maine and Idaho, two states with high potato industries, still have high ratios.

Map from Food environment atlas