I've noticed (American TV show) where suitable young offenders...

I've noticed (American TV show) where suitable young offenders are sentenced to a reeducation boot camp (tough love) instead of jail. Seems like a reasonable option to limit recidivism. I'm not sure about the success rate, but if the tough love approach was combined with some business/trade training towards a qualification, so these kids can make an honest living I think it would be a cheaper and more effective option in the long run than jail time.
As for the irredeemable (unsuitable) rapists and murderers - well I'd just parachute them into Afghanistan and have done with them. Now there's a cheap deterrent. Maybe even a few politicians too, like Trump for a lesson in hardship and humility.