My proposal is deliberately very brief so that you can further elaborate on it yourself. Instead of the current one-size-fits-all penalty, we could change this by regulating the penalty according to the price class of the car being driven at the time of the police officer's ticket.
 
The proposal is intended to punish offenders as equally as possible across the pocket. If you are on the minimum wage, a fine of EUR 100 is already a lot; whereas it is not so much if you are on five times the minimum wage. Usually, people choose a car that suits their financial situation, depending on their standard of living. Given that the judiciary, because of the non-connection of the records of the tax administration, the police and any other competent authority, does not allow the regulation of penalties by income, because they would not be able to establish the amount of the penalty at the point of the offence, the proposal seems to make sense, at least as a temporary measure that helps a little bit to be fair about the amount of the penalty.
 
Appendix:
Penalties could be higher on top of previous penalties; if you have a previous record with the police for any offence/crime etc. further traffic penalties would be that much more severe(higher amounts for offences etc.).