The demolition of Sydney's Allianz Stadium will cost taxpayers just under $40 million, leaving $689 million in the budget to rebuild the venue at Moore Park.

Infrastructure NSW chief executive Simon Draper revealed the figure at a budget estimates hearing on Thursday.

The NSW government had allocated $729 million for the controversial project, which has been under intense scrutiny since being announced in 2017.

In July, it was revealed construction giant Lendlease – which is knocking down the stadium – walked away from the second stage of the project.

It was reported at the time the government wanted the company to reconstruct the venue for less than the company thought feasible without cutting corners.

Asked about the contract saga during Thursday’s hearing, Premier Gladys Berejiklian insisted it was not “unusual” and that it was the government’s “prerogative” to reject Lendlease’s estimated cost to re-construct the stadium.

“There was a clause to suggest that if Lendlease did not meet government requirements, we could go back to the market,” Ms Berejiklian said.

“It’s our prerogative to make sure we get the best deal for our residents.”

Two construction companies – Multiplex and John Holland – are now in the process of preparing their bids for the construction phase of the project.

Lendlease will continue to oversee demolition work of the stadium, which the government previously said was on track for completion by the end of 2019.

The entire project is due for completion by early 2022