AS THE world commemorates the 10-year anniversary of the September 11 terrorist attacks, Australia's bill for fighting terrorism edges towards $30 billion, and local analysts are questioning whether we are getting value for money.

The $30 billion figure is an estimate, based on expert analysis of Australian spending on the wars in Iraq and Afghanistan, and the rivers of cash poured into police and intelligence agencies, and other security measures since the September 11 attacks on the US.

While the spending has been unquestioned by political leaders, analysts are asking if it is time to re-assess whether the risk warrants the expense.

Their concerns come as Prime Minister Julia Gillard prepares to reaffirm Australia's military alliance with the US at a ceremony in Canberra tonight.

Ms Gillard will tell those gathered, many of whom will be relatives and friends of the 10 Australians who were killed in the attacks, that she intends to forge even closer military ties with the US in the shared fight against terrorism.