Flights between London and Auckland are up to twice as expensive when booking from New Zealand compared to buying return trips out of Britain.
A Herald survey of British travel agents and websites found return flights originating in London were vastly cheaper than NZ deals on equivalent trips leaving Auckland - with major airlines offering tickets as low as $1500.
House of Travel says travellers often need to first get out of NZ - such as to Australia - to get a good deal, even to other destinations.
Airlines are defending the disparity as a matter of demand and local market conditions.
An Air NZ flight from London to Auckland in April and returning in May, booked from Flight Centre in the UK, cost £852 - $1620 on the currency exchange rate at the time.
The equivalent flight from Auckland to London on the same days, booked through Flight Centre in New Zealand, cost $3189.
And even when adjusting for seasons - so both return flights arrive in spring from autumn - it was at least $600 more expensive to fly return from Auckland.
Flights out of New Zealand cannot be bought on Air New Zealand's UK website, and one-way tickets out of London are almost as expensive as return trips.
House of Travel spokesman Brent Thomas said the price discrepancy wasn't widely known by New Zealanders. His firm hadn't received any complaints, probably because travellers were unaware of it.
"But there are times we put our customers on flights to Australia to fly to the US or even further to the UK because that's cheaper than flying out of New Zealand."
Mr Thomas said he believed the fare difference was due to demand and seasons, but ultimately it was the airlines' decision what flights cost.
Annie Webster, who wrote to the Herald about the discrepancy, said it was fair that Air NZ wanted to attract tourists to the country.
But there were many UK expats who wanted to return home to visit friends and family, who in turn would be encouraged to visit New Zealand for a holiday, she said.
"Where's the level playing field? It sucks."
Ms Webster said the planes had to "go in both directions anyway".
An Air NZ spokeswoman said there was more demand for a return flight from Auckland to London than from London to Auckland.
"This is why the price for the journey originating in Auckland is higher than that from London. In simple terms, the most cheap fares sell out first on any airline operating to and from New Zealand."
She said the best available fare at any time in any market was always determined by a combination of passenger demand and flight availability.
Other influences on price included the cost of international travel compared to other goods in the local market, seasonal demand influence on price, currency fluctuations and competitor pricing.
In the past 10 years, the NZ dollar has become about 33 per cent more expensive for UK visitors.
In 2003, a pound was worth $3. Now it fetches less than $2.
On the 2003 exchange rate, the disparity in the Air NZ fares would have been $616, down from $1569 on current rates.
A Qantas spokesman said every travel market was different, with big variations in the competitive, economic and regulatory environment from country to country.
"Airlines have to match their air fares to local conditions, which is why a ticket sold in London will have a different price from a ticket sold in Auckland. This is true for all international airlines, as it is for global retailers and other international businesses."
Aviation commentator Peter Clark said a "fare isn't just a fare" - sales, seasons, cost of supplies and fuel, demand and how full a flight was all affected the price of a ticket.
A UK travel agent expressed amazement when told of the disparity.
"That's amazing, isn't it? It's quite common though. It's weird but I can't explain it; it's just the way it is."
Travel agents were not willing to haggle on price but offered to beat quotes from competitors.
Korean Air ($2259) offered the cheapest Auckland-London return tickets, followed by China Southern ($2614), Air NZ ($2768), and Malaysian Airways ($2854).