In my opinion the justice system should aim to convert criminals into productive members of society, and protect the rest of society from said criminals until they're fit for society again.

Since it's not a simple problem to solve, I don't have a better solution than "use common sense and take as many aspects as possible into consideration, and dont' forget to look at the big picture". Saying that money is the only thing that we can measure and so it has to be the basis of any decision is to pretend that it's a simple problem.