why have it price based??
If the govt's idea was to promote cars that have lesser green houe impact..then let them promote exactly that....
lesser the carbon foot print..more the discount!
And guess...which car will come on top....
anyway, i feel that by having the excise discount based on the car price is not a great idea, as manufacturer's will start compromising on quality...not visible quality but certain things like safety features(or quality of those safety features), build quality etc..... Remember not all car buyers are smart enough to log on to tbhp to find out tech details abt all available cars....most of them just go and buy the cheapest(one that fits there budget).
...my 4 cents..
Regards,