Recovering the Pike River mine drift could cost up to $51 million.
The Government has approved another $10.8m to complete the project as well as a $4.2m contingency.
The agency was set up in January 2018 to re-enter the drift of the West Coast mine with the hope of finding out why 29 men died in a series of explosions in November 2010.
The Government originally budgeted $7.6m a year for three years, totalling $23m. It then topped up the budget to $36m.
The cost has increased around 700%.
They would spend less if they gave each family $1.75 million.