Questions are being raised about the distribution of funds raised by the Sound Relief concerts in Melbourne and Sydney, after it was revealed that just over half of the proceeds will be going to charity.

Hundreds of thousands of music fans attended the simultaneous events in Melbourne and Sydney at the weekend to raise funds for Victoria's bushfire victims and those affected by Queensland's floods.

Australians gave generously, with ticket sales exceeding $8.8 million.

Advertising had said that 100 per cent of the ticket price would go to charity, while big-name performers including Coldplay and Kings of Leon waived their usual appearance fees.

But now promoters have admitted that some of the money raised is being used to pay for production costs.

It is estimated about $5 million will actually go to the charitable funds, while nearly $4 million will cover costs like hotel accommodation and sound equipment.

About 118,000 Melbourne patrons bought their tickets believing that all the $75 of the ticket price would go to charity.

The concert's website promised 100 per cent of the proceeds from the Melbourne concert would be donated to the Red Cross Victorian Bushfire Appeal.

In Sydney, half the proceeds would go to the Bushfire Appeal and half to the Disaster Relief Fund for the victims of the Queensland floods.

Promoter Michael Gudinski, who heads the Frontier Touring Company and organised the Melbourne concert, was unavailable for comment.

The PR company representing Sydney promoter Michael Chugg did not respond to ABC's request for comment. The Red Cross preferred not to say anything.

Victorian Premier John Brumby is confident though the money raised will be distributed appropriately.

"The organisers made it very clear at the start that all of the artists and musicians were appearing free of charge," he said.

"They were donating their services, but there would nevertheless be some costs, for example in terms of organisation and hire.

"So they'll produce a full, orderly set of accounts and I would expect the maximum possible would be donated towards the fund.

"I don't know whether that would be $3 million, $4 million, $5 million or $6 million."

- Based on a report by Samantha Donovan for PM.