Auckland's three days at level 3 would have cost the city about $150 million in economic activity, according to a leading economist.
But the city's Mayor says the costs will be far greater if the coronavirus isn't stamped out quickly.
More than a dozen cases of COVID-19 have been found so far, all linked to a single yet still unknown source. More are expected to be revealed at 1pm on Friday, and a decision on the city's near future is due at 5:30pm.
Health Minister Chris Hipkins on Friday morning said he's seen no reason yet to go to level 4, but the situation is constantly shifting.
"Level 4 knocks out about a third of economic activity - that's the activity that cannot take place," ANZ chief economist Sharon Zollner told The AM Show. "Level 3 knocks out a bit under 20, so there is a pretty significant difference between those two levels and the amount of stuff that actually can go on."
With a third of the population, Auckland is the engine of the New Zealand economy. With 20 percent of it out of action, Zollner says a "back of the envelope" calculation puts the immediate damage at $60 million a day - with the restrictions coming on at midday on Wednesday, that adds up to about $150 million.
And it could be a bit worse, with many businesses legally able to operate under level 3 perhaps not bothering.
"A lot of restaurants for example won't bother offering a takeaway service if much of their actual offering is really the experience, as opposed to the food - that higher-end, for example."
Mayor Phil Goff says it was "always inevitable" a new outbreak of COVID-19 would happen in Auckland, since that's where the majority of people and freight from overseas comes into the country.
"We relish the fact that we were COVID-free for 102 days and life was back to normal, which made Auckland - and New Zealand - almost unique in the world. But sadly this has come to pass. What's really important now is we respond as quickly and effectively to contain the spread of the cluster."
He said it's good we're at level 3 and not level 4, as the city's much-needed construction work can continue.
"But undoubtedly this does have an economic impact. I've been talking today to the Minister of Finance about what the impact may be to jobs and incomes."
Finance Minister Grant Robertson, who set aside $14 billion in case of a second outbreak, on Thursday said he's looking into extending the wage subsidy scheme - something the Government had previously ruled out.
"If we do need to extend these restrictions, our hope is that it won't be for very long because we are getting on top of this single cluster."
Goff told Newshub the better-than-expected economic bounceback after the previous lockdown ended gave him hope the damage this time around would be limited.
"Going back to level 3 is a step back for our businesses and for council itself. We know however why it may be important to do that, but we hope that by acting early and acting effectively, we can restrain what the impact of that might be economically on Auckland if we had to go to a higher level and for a much longer period of time."
Whether he asks for targeted assistance for Auckland will depend on how the outbreak progresses, whether it extends outside of the city and the response from the Beehive.
"A lengthy period would certainly impact quite heavily on the city and we'd be looking at a range of options for the Government to provide assistance, taking that into account."
But he is confident the team of 1.6 million will prevail.
"We've defeated this before - by working together, by going early, by going hard, we have stopped the transmission of COVID-19. That's what we need to do again."