What a load of hot wad.
Generally, the more someone pays for a car, the less likely it is to be driven on a regular basis, and therefore has next to no effect on resources/emissions (not that regular use makes a lick of difference, but anyway...)
Where's the disincentive for someone not to use a thumping great 6-Litre, planet-raping, baby seal-clubbing, SS Commodore ($44,990) as a daily driver??
the key will be how the 'may' bit is determined (like, more than 1 car per year)...