The David Bain prosecution cost Crown Law $1.2 million, MPs were told today.
Solicitor-General David Collins told Parliament's justice and electoral select committee that the cost covered from 2006, when the Privy Council agreed to consider the case, until May 30.
Costs covered included pre-trial and Privy Council hearings as well as the recent lengthy trial.
The trial, in which Bain was found not guilty of killing his family, concluded on June 5, so costs would be slightly more.
"That is the cost involved in the prosecution of the case," Dr Collins said.
Mr Bain has received more than $2.7 million in legal aid since his original trial.
Labour MPs David Parker and Jacinda Adern quizzed Dr Collins about how Crown Law planned to managed a reduced budget while prosecutions continued to increase.
Dr Collins said it was hard to predict the number of prosecutions and how much they would cost.
It would be seeking a budget top-up this year to cope, and had had to do that the past three years.
Staff were working "long hard hours" to meet caseloads.
Ms Adern said there were 600 new police being recruited and in the past budgets were increased to match expected increased pressure on the service.
"I can't reconcile your explicit statement that you are getting increased demand, an increase in police numbers, and a decreasing fund."
Dr Collins said it would have to be very carefully managed.
"I anticipate at the end of the next financial year we will be seeking an increase in the appropriation, because if there's an increase in the police force this year the knock-on effect for criminal trials in the district and high court will take effect 18 months, possibly even two years, afterward."