So what...... every decision has to be a cost-comparison one? How would you equate the worth (I terms of cost per year to keep the inmate locked up) of locking up murderers vis-a-vis the "cost"/"worth" of one victim's life?

Okay, I'll play your silly game: If the cost of locking up someone is more than the cost of the damage that person done, then let's lower the cost of the locking up then!

No public sector union for the guards.
Buy crappier (cheaper) food.
Cut their internet and cable.
Get rid of expensive buildings and make em sleep outside under a poncho. I did it for most of my Infantryman life - I horrid weather to boot. (Ever visit Andersonville???)

There are tons of ways of making prisons cheaper before we talk about overcrowding and letting the little criminals go free.