For many people into fitness and/or nutrition hitting protein requirements is one of if not the biggest grocery costs.

The cost of 100g of different food products is not so important when the percentage of that 100g that's fat, protein, water, bones, etc varies substantially.

I think such a simple feature, sorting by protein per gram, would be extremely useful for a big demographic.

And bonus feature would be to filter by complete proteins, though I understand that would be a lot more difficult as it's not in the nutrion label information.