I think average people would thing that they would be too high for the crime.
Minimum day fine for someone without income is 6€. Now parking fine is I think depending locations is 20-80€.
So you tell that this incomeless person parked the car. And we have set it at 5 day fines so 30€ at low end. On other hand day fine for median earner is around 35 €. Which would mean 180€ parkin fine.
Alternatively, provide two values and select whichever is higher e.g. "30€ or 1 day", this method is common with corporate crimes (e.g. "1 million or 1.5% global revenue", that sort of things). Even if you're on the low end of incomes a day in jail would hurt a lot for a parking fine.
Parking fines, is bit more complicated. Maybe the tax rate of the car or some current price... Then again rich could get cheap car and just use that.