If I make $10/hour and you take $100 from me you’ve taken away 10 hours of my labour. If I make $600 an hour and you take $100 from me you’ve taken away 10min of my labour.
The $100 is equal but the impact is not. Fines are penalties, they don’t represent the cost of something - and a fixed fine is an un-equal penalty.
Your analogy makes some sense, but since wealth and contribution to society aren’t actually linked in reality - only in theory - I can’t get behind it. The wealthiest people in reality are parasites, not those who contribute the most. Owners not builders, CEOs not scientists, money managers not teachers.
I think it's important to remember that money represents debt. When someone commits a crime, they owe a debt to society. But if they have money, that means society owes a debt to them, so when they pay the fine it balances out.
The system isn't perfect but the idea is that if someone makes a big contribution to society, like by practicing medicine or creating new technology, society's debt to that person shouldn't be cancelled out by a minor offense like a parking violation. But if they aren't contributing much, then breaking the rules could make them into a net negative.