Figures released by the Australian government show that the detention centers for asylum seekers in Nauru and Papua New Guinea cost more than 265 million US dollars.
An immigration department official says 1,637 people had been held in the two centres and the expenditure was for the period September 2001 to the end of June last year.
This means the detention cost about 2,300 US dollars a week per individual.
Aid and human rights groups, such as Oxfam and A Just Australia, have previously estimated the total cost of the policy at just under a billion dollars.
The government, which was elected last year, ended the processing of asylum seekers in the Pacific and allowed all remaining refugees on Nauru to be resettled in Australia.
Staff at the centre are expected to be offered severance packages by the International Organisation for Migration, which administers the offshore detention centres on Australia's behalf.