Germany does this, for example. Criminal fines are set by the judge in "daily rates", and 30 of them make up the defendant's monthly income.

Over there the judge has some leeway for creative sentencing. I remember this case where one fellow ran the numbers and figured it would be cheaper for him to pay the occasional fine for parking in a no-parking zone than pay the parking meter. This didn't go down well with the judge, he argued that road signs are not made to look pretty, they serve to regulate traffic on the public roadways. That fellow had to hand in his license, he was banned from the road for five years, and a re-application after a ban involves a chat with a traffic psychologist.