A friend of mine (who is brilliant, but also an asshole) once shared with me a part of his philosophy on life. This occurred as we were staying in adjacent hotel rooms. There was an after-wedding party going on in his hotel room, and he lights up a cigarette. I mention to him "Hey, you know there's no smoking in DC hotels, right?" to which he responds "Yeah -- it's allowed." Pretty confident he was wrong, I kept at it, until he pointed out that it cost $150. Not understanding, I questioned him, until he broke it down -- it's not allowed, but for violating the rule, the fine is $150. For him, celebrating the wedding of our close mutual friend was a festive occasion, and worth paying the $150 for.
In short, he had deemed that the fine was not a fine, but the cost, and he was willing to pay it.
If laws are prohibitively expensive for the poor, but merely 'a cost' for the more well to do, then we run the risk of jeopardizing the rule of law entirely, and begs the question of whether or not the law needs to exist if nobody is harmed by its selective infraction. Liability already covers means for reliably determining who is at fault, so where there is incident, the person running the light can be considered at fault. Otherwise, it seems to be just a system for generating fees, and largely from the hoi polloi.