An Australian inquiry into child sex abuse heard on Wednesday that the nation's former top Catholic cleric, now Pope Francis' finance chief, tried to bribe a pedophile priest's victim to keep him quiet.

David Ridsdale, who was abused by his priest uncle Gerald Ridsdale, told the royal commission that he confided in Cardinal George Pell about the sex assaults in 1993.

"I told George I had been abused by Gerald. His first reaction was 'Oh, right'," Ridsdale told the hearing in Ballarat, Victoria, alleging that Pell went on to ask how much it would cost to buy his silence.