While I think one or two packets of ketchup or mustard should be included at no charge for a sandwich or order of fries, I'm wondering if "hot" mustard is something special, like a dipping sauce for the chicken nuggets, maybe? Those dipping sauces are intended specifically for the nuggets, and probably more expensive since you get more in those little tubs than in the plastic packets. Maybe they buy extra to have on hand for customers who like to dip their fries or add it on their sandwich. In that case I think an extra charge of a quarter is reasonable.