The V8 Supercars will be a financial boon for Auckland, and the man behind the publicly funded plan says he has the figures to prove it.

Some city leaders have slammed the return of the V8s to Pukekohe Raceway next April, the first time since 2007, after its five-year stint in Hamilton landed ratepayers with a $40 million bill.

They are unhappy the public purse will be dipped into again, with the Government pledging $2.2m and a divided Auckland Council finance and strategy committee voting to spend $10.6 million of ratepayers' money over five years.

However, Auckland Tourism, Events and Economic Development chief executive Brett O'Riley said the event would pump $7 million back into the city each year, based on a projected 50,000 visitors coming to the city.


He promised that those figures were not inflated.

Economic consultants Covec, who crunched the numbers on the value of the event for Ateed, had taken a conservative approach, O'Riley said.

The economic benefit was based on how many attended previous V8s in Hamilton and Pukekohe, and how long they had stayed.

"People in the events business have said our figures are conservative, especially given that we have only forecast the same number of people attending each year and given [the event's] longevity."

Covec had a good record of not overselling economic gain, he said. It had predicted the ITU Triathlon World Cup would boost the city's coffers by $491,000 and the Champions Trophy hockey tournament would bring more than $1 million.

The two events did better, injecting $520,000 and $1.4 million respectively. However, the $5.9 million economic gain from the Auckland stopover of the Volvo Ocean Race fell a whopping $4.8 million below expectations. That was because the number of expected boats fell by four and poor weather halved the time the boats were in Auckland, O'Riley said.

Actual economic gain was calculated after each event by surveying participants and punters on where they had come from, how long they stayed and how much money they had spent.

"We want to leave no stone unturned if we are going to spend ratepayers' money," O'Riley said.