Well, it's all linked isn't it really, society is one whole chaotic system. Does better education, better understanding of mental health conditions lead to less people in prison, less cost on that front. Cause and effect. You can't necessarily pull money out of education, out of public services...
Where they can be assessed, watched, looked after, medicated, call it what you will, by specialist professionals trained in dealing with mental health conditions. I think that is the point rather than picking out whether there are violent persons in both normal prisons, or secure mental health...