I think this is an important point. These costs are amongst the many things a judge should (does?) weigh up in sentencing. If she gets it wrong a sentence may be reviewed (made more harsh or lenient as appropriate) on appeal. However when sentencing is politicised, such as with mandatory sentences the judge's "judgement" is taken out of the equation. It may be appropriate to give a guy life for stealing batteries when a bigger picture is taken into account but that should be for the professionals (i.e the judiciary) to decide rather than politicians looking to buzz frightened people into voting for them.