Fines should be punitive in nature but not excessively. Rich, poor, male, female, straight, gay, all should be treated the same.
I think fining the rich more because they are rich is not the way to go about it. Should we charge them more for their leisurely items? It's about choices at the end of the day. If you are worried about not being able to feed your family because of a $50 fine then don't speed! It's not something people do against their own will or because they have to (bar being late for work which I would argue isn't an excuse anyway.) That's the point of the fine: to put people off doing it.
If poor people are deterred from speeding because of the cost of the fine, then why are we talking about poor people getting fined at all, after all they wouldn't be speeding.
Just because someone has money it does not mean they will flaunt the law because they can afford the fine.
In both cases correlation does not imply causation.
Where demerit point systems are in place both poor and rich lose their licenses after too many infringements.
Apparently, it does:
"It is generally the case that people getting less absolutely risk averse as they get wealthier."
http://marcfbellemare.com/wordpress/2012/02/speeding-fines-t...
A points system is interesting, but of course, it ignores accessibility and cost towards inevitable lawyers.
They aren't and for a reason. Otherwise the rich would pay the same (small) amount of tax as the poor.