The actual cost is around $270 per day or an average of $295,168 for a three year sentence. ABC news Sep 17, 2015: source Ombudsman report. So I suspect my $100k estimate provided by the head of a prison, is accurate.
44.1% are re-offending within two years of release.
Corrections Victoria budget is $1.04b p/a]
You need to quote the whole finding in the Ombudsman's report and account for infrastructure costs, not just direct costs.
"The cost of the prison system continues to spiral. Since 2011, the budget for correctional services in Victoria has risen by 31 per cent to $1.04 billion.
And this excludes a further $670 million committed to the construction of the new Ravenhall Prison and the estimated $1.6 billion required to operate it for the following 25 years"