of course..., I'd like to see them do an environmental impact study on producing a new car versus driving an older one 5 more years.
Probably why the extra cost is 'only' $42. Depending on the condition of the car and driving habits, break-even for an older car vs building a new one a bit earlier might come sooner than you think. Smog is only only one type of pollution, a car with otherwise borked emissions can put a lot of crud in the air.
I remember reading somewhere that in California the newest cars actually clean the air, while older cars can pollute as much as 1k+ newer ones.
As for Dubai, I figure they'll probably set it equal to the citizenship income level. They're one of those countries where 75%+ of the inhabitants are actually immigrants, not that they grant citizenship easily(or at all). They pay a divident of oil income to all citizens, though the royals get the lion's share.