Manus Island detention centre.
A report by UNICEF and Save the Children found operating the detention system on Nauru and Manus Island had cost $3.6 billion since the reintroduction of offshore processing in 2012.
The report said shutting offshore detention facilities would save $2 billion over four years.
Turnbacks are estimated to have cost nearly $300 million since Operation Sovereign Borders began.
The government has also spent $40 million on the failed Cambodia resettlement scheme and $275 million on "regional cooperation activities", which the government gives to countries in the region to “encourage” them to deter asylum seekers from attempting to get to Australia.
Like the article? Subscribe to 鶹ý now! You can also us on Facebook and on Twitter.