I work with a lot of mid 6-digit income people. I guarantee you that the fines are a deterrent for them. A $100+ ticket definitely puts a damper on the rest of their day. However, the insurance demerit strikes and the licence demerit points are probably the bigger deterrent. I have no problem with actually enforcing these demerits, instead of the usual go-to-court-and-get-your-demerit-points-waived-just-for-showing-up practice that is the norm now.
Ironically, I wouldn't be surprised if there were proportionally more speeding tickets amongst my acquaintances when I was a poor student than now, even though my acquaintances are much more wealthy than they were when I was a student obviously. ie. I don't know for sure, but I suspect for speeding there is a higher correlation with young age than there is with high wealth. If this is true, there is actually more justification to have bigger fines for the young than there is for the wealthy. Supporting this is the commonly cited statistic that the car accident rate is higher in very young drivers than middle aged drivers.
Like I said, the income-based traffic fines scenario is simply fodder for the class-warrior, to make a few less wealthy joe schmoes and a few bureaucrats feel better.