In my line of work, I’ve had too many questions about exactly how much something will cost. In the context, it’s like the answer to “How much does a car cost?” – depends on the type of car, and its age, et al. Or how much does a house cost? I can find housing trends in an area but that doesn’t mean house X will sell for Y dollars.
I had someone ask for the exact cost per mile for driving a car. As it happens, I had figures for one of my cars — the only one I ever bought new — and so I coughed up the figure (59 cents per mile), with the annotation: “If you drive exactly the same car as I did, get the same mileage as I did, and subsequently wreck it the same way I did, these numbers should be valid, depending on your state’s gas tax.”