Last Sunday the Top Gear team set themselves a challenge to buy a used car that could be converted into a car that could be used by the police. The point was that if the police bought used, second-hand cars they wouldn't be as worried about wrecking them, and would be able to take a more "active" approach to apprehending criminals in cars.
I was reminded of an interview I did with former Royal Mail CPO Ninian Wilson. He explained that Royal Mail had had a problem with their vehicles not being treated very well by employees. So the procurement answer was to buy better vans and cars, because if they liked what they had, they would treat them better.
So although the Top Gear team's method would save money on the cost of the cars, the total cost of ownership would probably be higher.