One of Auckland's biggest rental agencies hiked rents on vacant apartments by five percent a week for several weeks earlier this year when demand from students surged to record levels.
Ray White agent Krister Samuel said demand for apartments was unprecedented in February.
The seasonal surge was caused by thousands of tertiary students and was exacerbated by a big rise in first home buyers snapping up apartments, shrinking the rental pool, he said.
"We were getting 30 to 40 applicants turning up to a one or two-bedroom apartment, and all with good credit history, and testimonials and landlord references.
"So the only response was to put the rent up," Mr Samuel said.
"For the landlords that we were representing, and we represent about 1000 individual landlords in the city, we were putting the rent up about five percent a week, week on week for about six weeks."
It meant that two bedroom units that started the year at $400 a week were being let for more than $500 by the end of the seasonal rush.
Raising the price was the best solution for tenants and landlords, Mr Samuel said.
"We're in business so our job for our individual landlords is to firstly provide them with a vetted tenant who's going to pay the rent and not cause any damage to the property.
"Secondly, these are investors who purchase these properties to fund their retirement or fund their lifestyle ... so our job with them is to get them as much as possible with a quality tenant in place."
Rent hike was price gouging - property investors' association
Auckland Property Investors' Association head Andrew Bruce called it price gouging.
It caused resentment and no one won, he said.
"Tenants aren't stupid. They'll go off and once they've found an affordable place or a property at a market rent they'll give their three weeks notice and you could potentially have vacancy," he said.
He preferred to let a place just below market rental to a good tenant.
Auckland University Students' Association president Will Matthews said the figures were shocking and international students were hardest hit.
He blamed the high rents on Auckland council and the government for failing to tackle the accommodation shortage.
"Landlords are raising their prices to meet demand and I think that certainly there should be some way of ensuring that prices don't just rise exponentially well above what students - or anyone, can actually afford to pay," Mr Matthews said.
Landlord Andrew Bruce said students should try to avoid price spikes by securing accommodation at the end of the year.
However, Mr Matthews said it was unrealistic to think that students could afford to stay in the city during the summer break to get cheaper flats.
And despite thousands more apartments being built in central Auckland, it may not ease pressure on accommodation, Mr Samuel said.
"Talking to the major tertiary providers in the central city, they're actively encouraging higher student numbers so if they fulfill their demand goals and get more students coming into the city, even though the supply is coming on stream, it still may be the same," he said.