Hoe do you get your figures

Looking at the Estimator tool, it appears to not differentiate on this item between gasoline and Diesel engines. This could be an explanation for the majority of your concern. My thoughts are that $25.00 is a bit on the high side for VC7B coolant from Ford. $125 at the dealership level all day long for a conventional cooling system flush is reasonable. For a Diesel, you would add an additional gallon of coolant.