My uniforms when I worked for the US military were made by people we US citizens enslaved (glad to see other references to the 13th amendment here); I am not proud of that fact. I learned about it in school, as a teacher sitting in on a class taught by the social studies teacher.
If I were in prison I would want: A sense of hope that I could learn and grow and continue to be a full and dignified human until I die. To this end, counseling, teaching, work that pays fairly, and general social, emotional, and intellectual rehabilitation within my zone of proximal development (teacher jargon per Lev Vygotsky) would be appropriate, and worth taxpayer expense, regardless of what I did to end up in prison.
Frodo told Gandalf he wished Bilbo had killed Gollum when Bilbo had the chance, and Gandalf said no- we don't know what good anyone might do in their lifetime. This convinced me that the death penalty is wrong. Banishment is better, and even better with rehabilitation efforts. I accept the risk that a relative few people in a well-designed system will still do more harm than good.