Seems to me that prisoners could be considered slaves without them even lifting a finger to help pay for the $26,000 a year (or more).
http://dictionary.reference.com/browse/prisoner
1. a person who is confined in prison or kept in custody, esp. as the result of legal process.
http://dictionary.reference.com/browse/slave
2. a person entirely under the domination of some influence or person
3. a drudge
http://dictionary.reference.com/browse/drudge
1. a person who does menial, distasteful, dull, or hard work.
2. a person who works in a routine, unimaginative way.
http://dictionary.reference.com/browse/prisoner
1. a person who is confined in prison or kept in custody, esp. as the result of legal process.
http://dictionary.reference.com/browse/slave
2. a person entirely under the domination of some influence or person
3. a drudge
http://dictionary.reference.com/browse/drudge
1. a person who does menial, distasteful, dull, or hard work.
2. a person who works in a routine, unimaginative way.