> So perhaps charging much more for food over 2,000 kCal/day per person makes a lot of sense.

Why financially penalize exercise? Even physical activity aside, why do you think everybody needs exactly 2,000 kCal/day to maintain their weight?

What about tall people or people with abnormal metabolisms? I require more than 2,000 kCal/day to maintain a normal weight, even when completely sedentary. Why should I suddenly have to start paying more per calorie past 2,000 kCal?