Serco is billing the State Government almost $1 million a year for seven court and custodial security officers to staff the Kununurra court complex.
It includes some staff on fly-in, fly-out arrangements.
The Opposition says the arrangement is another example of how Serco's custodial services contract with the Government fails to deliver value for money to taxpayers.
But the Government and Serco say they have been forced to hire fly-in, fly-out workers because it cannot find locals to do the job.
The seven security officers at Kununurra cost $903,000 a year - an average of $129,000 each.
This compares with $372,000 for five security officers at the Carnarvon courthouse, at an average cost of $74,400.
"The discrepancy of $531,000 between staffing at Carnarvon and Kununurra is due to the two additional staff and costs for fly-in, fly-out accommodation and meals," Attorney-General Michael Mischin told the Upper House in response to a question from Labor's Ken Travers.
Mr Mischin and Corrective Services Minister Joe Francis directed questions, including why locals could not be employed and whether the arrangements represented value for money, to the Department of Corrective Services.
"The department can advise that Serco does actively recruit staff locally," a DCS spokesman said.
"The retention of staff is an issue and to maintain a minimum staffing level to ensure service delivery, FIFO arrangements are in place and justifiable.
"Of the seven staff for the Kununurra Court, the contract variation cost (with Serco) allows for two FIFO workers."
Shadow corrective services minister Paul Papalia said the revelations confirmed Labor's fears that the Government had signed a poor contract with Serco in 2011.
"The taxpayers are getting ripped off," he said. "And it's made worse by the fact that we know that a lot of Aboriginal education assistants in Kununurra just lost their jobs because of the Barnett Government's education cuts.
"I have never heard of government employing fly-in, fly-out security people in a court in Kununurra.
"Certainly we wouldn't do it and I would defy any government to do it.
"Kununurra's a big town. There are a lot of people there."