It costs $317 per day - or more than $115,000 a year - to keep each prisoner locked up in West Australian jails, new figures have revealed.
And it is even more expensive to keep a young offender behind bars.
After a horror year for the state's Department of Corrective Services (DoCS), including a riot at WA's only juvenile detention centre, it has also been revealed that the cost to keep prisoners locked up has shot up in 2012/13.
With WA's prison population topping 5000 for the first time during the period, the daily cost per inmate has risen from $291 in the previous financial year to $317.
And with some juvenile prisoners still being kept in the adult Hakea prison after the Banksia Hill riot in January, the cost to imprison a young offender was $645 a day - or more than $235,000 a year - exceeding the target cost of $558 a day.
It costs more to detain a juvenile offender than an adult one because of staffing requirements.
For every eight young detainees, there must be one guard, but the ratio is much higher for adult prisoners.
The department's annual report revealed there were 11 escapes from WA prisons in the past 12 months, but none of them were the result of malfunction or damage to the physical security of a prison, and all prisoners were returned to custody within 24 hours - two on their own accord.
There are also now 16 dangerous sex offenders in the state being tracked by controversial GPS technology, just months after it was introduced.
New laws came into effect in February to allow GPS tracking of sex offenders classified under the Dangerous Sex Offenders Act.
And the department is considering extending the use of the tracking devices to criminals convicted of arson and serious violence, which would require legislative changes.