@aral It doesn't properly do what it's supposed to, but there's a model of "day fines" used at least in Finland where fines are based on the daily income of the person.

"10 day fine" -fine would be 450 EUR for someone earning 3000 EUR per month, and 4950 EUR for someone earning 30k EUR.

(There's a bit of nonlinearity at the low end of the scale due to deductions for living expenses.)

Should be based on the wealth and income both, then it would be much better...