It is now almost $40 cheaper for a gram of the Class A drug and there are "record lows'' reported in the Auckland, Waikato and Wellington regions, according to results in a survey released today.
The median price for a gram of meth is down nationwide - from $538 in the 2017-18 period compared to $500 in 2018-19.
The results are from the latest bulletin from Massey University Shore & Whāriki Research Centre.
Researcher Chris Wilkins said the lower prices seen in those North Island regions were consistent with their proximity to international smuggling routes - via airports, seaports and isolated coastlines; as well as the concentration of domestic methamphetamine manufacture in those regions.
"The higher prices of methamphetamine reported in Tasman, Nelson, Marlborough and the Southland/West Coast regions likely reflect geographical distance from production and importation sites and smaller, less competitive drug markets," he said.
Although prices in the South Island were said to be higher, there still appeared to be "substantial declines" in prices compared to the previous year.
"These declining prices for methamphetamine are consistent with record seizures of methamphetamine and reports of gangs expanding methamphetamine selling into rural areas and the South Island."
It is the second time this survey has been carried out and looks at trends over the past six months - particularly the drop in the prices of meth compared to relatively stable prices for cannabis, LSD and Ecstasy.
Wilkins said the researchers were surprised by the results.
"From previous surveys, we were aware [the] price was declining and we were really surprised to find record low prices just because we thought there's no way that could continue.
"But when you draw back a bit and look at the larger context, you can see how the results are consistent with record seizures and high reports of availability."
'That shows the power of the illegal drug market'
In the early 2000s, the price of a gram of meth was $1000, Wilkins said. It is now less than half that in some places and that does not account for inflation.
"That really shows the basic power of the illegal drug market."
The drug was now both cheaper and easier to get - which would inevitably lead to increasing use, he said.
Customs has trumpeted its record seizures of the Class A drug - and there have been some huge seizures in the past few years.
One of the most famous - or infamous - seizures in recent times was the more than 500kg meth discovered being smuggled into the country via Ninety Mile Beach, in Northland, in 2016.
Had it made it on to the streets, it would have been worth up to $500 million.
But Wilkins said international evidence showed the price was "where the rubber meets the road".
"If you have high levels of drug seizures [but] price is continuing to decline, that's telling you it's not having an impact."
He pointed to the crack cocaine epidemic authorities in the US dealt with in the 1980s.
Despite a huge amount of effort going into enforcement, the price of crack dropped significantly.
"The power of the market tends to swamp drug enforcement. I'm not suggesting we give up - the seizures are obviously a really good success story.''
Wilkins believes Customs needed more resources, but it was also important to focus on the health side of the meth epidemic - including making drug treatment and help readily available.
Providing alternatives for young people so they would not get into the Class A drug in the first place was also important, he said.
