So then the poors won't be able to afford cheap used cars because the rich will drive up the prices because they will want to buy them as commuter shitboxes. And then the fines will scale up in reaction to that increased value. And then everyone will be worse off than we currently are.

I'll be fine, because I already own all my shitboxes, but this is just bad policy.

Coming back to this... People lend their cars all the time - siblings, children, parents, etc. So you cannot pin who was driving the vehicle at the time of the fine. This is why red light cameras are a flat fee. They do not scale based on the number of tickets the car received. You would think that if someone received 30 red light cameras, it is time to increase the fee, but this is not cannot be accomplished without proving who the driver is.

>acceptable middle ground is for fines to scale with the value of a car at registration

The type of car one drives is not at all an indication of their actual finances. Many people, unfortunately, feel the need to impress others by spending money they don't have.