That is an interesting question. However, I believe that the sum of money an individual is prepared to spend on a "new" car is fixed to a certain extent. How economical that car will be, will be down to the individual. Depreciation and running costs are big factors, but the amount someone will spend, I believe is set. Most buyers have a figure in mind before they look.
e.g.
BMW 3 SERIES 3.0 325i M Sport Highline 2dr (59 plate, 84,000 miles)
Ford Fiesta 1.0T 100PS Titanium 5dr (65 plate 10,500 miles
Both cars cost £10,000 but running costs will be very different.