Attorney-General Chris Finlayson says the investigation and prosecution of the Te Urewera charges has cost police more than half a million dollars.
Four people were found guilty of several firearms charges at the High Court in Auckland this week.
But the jury was unable to reach a verdict on the lead charge of participation in a criminal group.
When the Mana Party leader Hone Harawira questioned Mr Finlayson in Parliament Thursday about the cost of the case, he replied that it had cost police $500,462 excluding salaries.
Mr Finlayson also said prosecutions between 2009 and February 2012 had cost $322,412
