Posting bail has nothing to do with being under arrest, and everything to do with remaining detained. For many (particularly non-violent) arrests there is no reason to detain a person until the time of their trial, which is at least a month but can commonly be a year or longer after the original arrest date due to a backlogged court system as well as delays necessary to prepare for a trial. Bail system does favor people that can afford it, but so does the trial system (afford a better lawyer), the healthcare system (afford a better doctor), the housing system (afford a better house in a better area), etc. That's called capitalism.
I agree with you that it does not make sense to detain someone for a non-violent crime unless they are likely to commit more crimes. But then they should be released unconditionally while awaiting their trial, not dependent upon whether they can pay a ransom fee or not. On the other hand a psychopathic murderer is dangerous to society so he should never have the option to pay bail.
The point is to give the defendant a proportionately strong incentive to show up at the trial. The judge has authority to set bail at a level that makes it likely they'll actually stand trial, which has to take into account the defendant's personal resources, the size of the potential punishment, and the level of danger they pose. If Bill Gates was being tried for first degree murder, I'm sure his bail would be set well north of $1 billion.
I could be mistaken, but I don't think the idea is to force poor people to be detained. I think the purpose is to provide an incentive for the accused to show up to their court date. If the person posts the bail themselves, then they get the money back when they show up. If they use a bail bondsman, then a bounty hunter will track them down if they don't show up.
Then why didn't this kid, and anyone else stuck in arrest that can't pay the bail, use a bail bondsman to get out of it? It seems like a reasonable idea but broken in practice. If I wanted to become a fugitive I wouldn't care of I was chased by both bounty hunters and the police.
You still need to pay the bail bondsman 10% of your bail (and you don't get it back). He probably didn't have a spare $50k. The question I have is why was the bail $500k? That seems excessive.
