It's got nothing to do with people of modest means. For them the fine would be what you would consider normal. It's the people of abundant means that the fines target. To a millionaire, there is no reason not to speed. A couple hundred bucks is nothing to him. Better for him just to drive 100 mph everywhere and look on the piddling speeding fines as fees for his time.
But when you scale the fine upward, this starts to get his notice.
Again, it's to keep the ultra rich from out-right flaunting the same laws that the people of modest means have to obey.
We do the same in America with progressive fines. Rich people are fined much more than poorer people just for being able to produce more. It's called income tax.
Rich people get points on their license that add up to suspension or revocation the same as everybody else does. That's plenty of reason not to speed, and it works fine.