How does penalising cost less than rehabilitation?
There are costs associated with any rehabilitation program. It costs money to hire teachers, buy equipement, provide space for training and so on. Cutting the programs seems like an easy way to save money.
But it's a false savings and not just from lower recidivism rates. Rehabilitation and training programs keep prisoners busy and help them learn to work with others. You end up with fewer fights and other problems between the inmates.