On the contrary, the point is to correct for that fact that a flat-fee fine is a complete non-issue if your income is high enough. There have been times in my life when an accidental or unexpected $50 fine would impact my ability to pay rent or other essential bills that month. But now I'm not even sure I'd bother going to court to contest something that small because I just wouldn't care enough to spend the time or emotional investment.
It's actually the other way around. It's high enough to not be economically viable for anybody.
If a person's income is low enough that probability of being fined * percentage of income per fine * income is less than price of parking, then it's economically viable for them not to pay for parking and risk the fine.