I would argue if the goal is justice then the fine is basically a tort on the externality imposed. At some point society imposes an injustice if the fine exceeds the externality imposed by tailgating, even if it's a pittance to the rich person.
That is, for justice rather than just retribution, I think the real nominal cost of tailgating is probably not closely linked to wealth or income of the offender
But the point of the fine in this case is clearly not restitution, but disincentive. Justice in this case is ensuring everyone is equally incentivised to follow a law that society thinks everyone should follow.
If the goal were only to ascribe economic harms to certain actions and reclaim those costs, it would be called a tax or a fee, not a fine.
some people will never understand and at this stage i think its pointless.
Lets have a look at two examples of parking in a disabled person space
if you make 30k a year, have no savings, $100 is major expense.
if you make $1m a year, $100 is just a vip parking space.
Both people should be equally de-incentivized to illegally park in a disabled people parking spots. The proportional fines are the only way to get close enough to that state.
Instead of being the discretionary income of this philanthropic rich guy who would graciously give it all away to his servants, those 100k go to the Swiss government, which famously provides no public benefit or services and in fact just sets the money on fire
It's fair to say and, on some level, I like the idea of scaling fines to lower income more than scaling them to higher incomes. The marginal utility of wealth goes down as you get more anyway.
I also think that, if you wanna critique the efficacy of fines in metting out justice, you need to go further than you do here. Scaling the fine tries, imperfectly, to match the punishment to the circumstances of the offender. We could imagine an even better system that more perfectly reacts to misbehavior, but exactly what that would be seems hard and this is a sensible adjustment to an existing system.
That is, for justice rather than just retribution, I think the real nominal cost of tailgating is probably not closely linked to wealth or income of the offender