Salvage luxury cars are not cheaper than salvage economy cars. What affects the discount on a salvage vehicle is the extent of the damage and why it was given a salvage title. Cars that are stolen and then later recovered are often given a salvage title. These vehicles will not drop in value near as much as a car that was totaled and than rebuilt. A salvage title vehicle will lose anywhere from 10-60% of its value depending on the damage. Salvage title vehicles can also be harder to sell, so it is a good idea to seriously consider the wisdom of buying one of these cars.
For more info, see How to Buy Salvaged Vehicles from Insurance Companies