I think good mileage is important.
I also think the price of the rig is important.
So is the cost of everything else we use in life.
Why differentiate? It's all part of the equation.
I can't understand those who always recoil when someone asks the question about mileage, implying the question is silly. I don't see the same reaction when someone asks about the price of the rig itself.
Another reason that good mileage is important is the depletion of a finite resource, oil. I'd like to leave a little for my grandchildren in the small ways I am able to do so.
I won't mention the environment.