I dislike this "the fine isn't that much because he earns so much" argument that comes up. Should people be fined more for speeding because of how much they earn? You hand out the punishment to fit the crime. Not to fit the defendant.
Once I, er, my friend had to go to court for a minor driving offence, and the judge wanted to know how much I, er, he earnt in order to decide upon a suitable level of fine.