Food nutrition spreadsheet highest nutrient value per calorie?

So I would like to know what the top foods are high in a particular nutrient, but relative to the calories.

For example Cashews are high in iron, but they cost 31 calories per gram.
Lentils only cost 13 calories per gram of iron.

But since I'm looking in the kitchen, thinking of a recipe, or adding to a grocery item I want to pick from a list of best value for your calorie.

It is tricky though. I downloaded the USDA food database but started with the brand items database - tricky due to many duplicates, multi ingredient items, inaccurate values etc.

Later perhaps I'll try again using the Standard Reference database.

What do you think of the concept? Its a little geeky I guess.