It's actually around $220k now and the likelihood of any sort of rehabilitation inside is remote as revealed by a recent audit of Corrections Victoria.
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.