I don't think it's far-fetched at all. It would be their immediate families. If my son went to jail, I did something wrong somewhere whilst parenting. Are you stating that everyone as a whole should pay for the criminals as opposed to the mother/father etc of the criminal? Fuck that. Why should I have to pay for their bad ass child if they don't want to? Perhaps if people know their loved ones will suffer if they go to jail, they'll stop doing stupid stuff to get put there. I'm sure Bob Criminal doesn't want his wife to have to take four jobs to afford to keep him in jail, so maybe he'll straighten up and fly right. I'd rather my taxes go to pay people's hospital bills rather than their jail stay. Plus they can enforce that it's bad off. While on parole they have to have a job. So, they have to pay a portion of that to their jail stay. If not, they garnish their wages. They do that for child support, do it for their jail stay. And if they don't pay, they go back to jail and accumulate a larger bill. Their life is ruined. Who cares? They shouldn't have been doing whatever they did to get there in the first place.
and again while i agree in principle that if you're a parent and your kid fucks up it is on you. but there are plenty of occasions where a parent does everything they can to raise their child right and he/she still turns out bad. the parents aren't always at fault in cases like that. and waht happens in the case of a person who has no immediate family? who pays for their jail time? and your idea doesn't even touch on the people who end up in jail for crimes they didn't commit. is it right to not only throw someone who is innocent in jail, but make them pay for their own jail sentence as well?
i really do agree with your idea in theory, it sounds great, but i just see too many holes in it for it to work well.
(just to note, i'm not trying to attack you or say you're wrong about this, just trying to debate the ideas here. so lets not get worked up and upset at each oher like you and i have a tendency to do in topics like this, ok? )