The total government outlay for the investigations over three years from 2013/14 comes to $260.3 million, the federal budget papers show.
A royal commission into union corruption set up by the coalition government, and which will report in December, is expected to cost $53.3 million.
The funding will come from savings in the employment, industry and infrastructure departments.
Another inquiry into the Rudd government's home insulation scheme is expected to cost $12.2 million, while the royal commission into child sexual abuse will cost a total $211 million in 2015/16.
The previous Labor government initiated the child abuse inquiry and has labelled the two other royal commissions "witch hunts".
Treasurer Joe Hockey has said the inquiries are necessary.
"We've got a more transparent system in a range of areas and it will improve the quality of government," he said.
The funding includes paying the legal costs of many of the witnesses to the inquiries, according to the budget released on Tuesday.
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