But they say the figure pales in comparison to the cost of abuse in the community in terms of homelessness, mental health treatment and drug and alcohol abuse.

The release by the commission of a major discussion paper on redress on Friday brought a sharp intake of breath from some after it was revealed that such a scheme could cost $4.37 billion over 10 years.

In reaching its headline figures, the Royal Commission into Institutional Responses to Child Sexual Abuse assumed an average payment of $65,000 for each victim.

The costs would equate to $1.971 billion from government, $582 million of which reflects government's contribution as "funder of last resort" – its role in backing up institutions where abuse occurred but which now had no money to pay.

Private institutions would be required to contribute $2.4 billion.

But some advocates for victims and survivors said the total cost of a just redress scheme could be considerably more than that estimated by the commission.

The President of Adults Surviving Child Abuse, Cathy Kezelman, said the $65,000 average figure was quite conservative given the impact of abuse on the lives of individuals.

This position was supported by the Director of the Survivors and Mates Support Network, Craig Hughes-Cashmore.

"The cost could be more – it's very difficult to know the size and extent of the problem," Mr Hughes-Cashmore said.

However, both advocates emphasised that the cost of inaction was far greater.

"When it comes to the bottom line we need to consider the enormous cost our community is already paying in terms of the public health and broader social impacts of child abuse," Dr Kezelman said.

Proposed changes to the burden of proof in civil claims made by the commission came  in for criticism on Friday, with some suggesting they may discourage people from volunteering for grass-roots organisations.

The commission suggested that, rather than victims having to prove that an institution breached its duty of care, as is currently the case, the institutions could be required to prove that it took all reasonable steps to care for the child.

Such a change would be controversial as it reverses the onus of proof that has been enshrined in civil law for centuries.

"We've got to be careful of major shifts in the law which drive people out," Patrick Parkinson, a Sydney University expert in responses to child sexual abuse said.

"We've got to think about local at our local soccer club. Because it's on the strength of our local organisations that our social capital exists – the volunteers who are so important to our social fabric."