Ruben enjoys a cheesburger from McDonald's in Grey Lynn, Auckland - but how much did it cost?

McDonalds has been caught out charging lower-income Kiwis more for their burgers and chips.

Customers in Porirua - home of New Zealand's first golden arches restaurant - are paying more for a cheeseburger combo than other stores, including those in well-heeled areas such as central Auckland.

The extra costs run across the board - with Porirua punters being charged 90 cents more for a Serious Angus burger when compared to the McDonalds in Grey Lynn, Auckland - one of the country's wealthiest suburbs.

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But the regional variation is no surprise to Canterbury University's associate professor of marketing, Ekant Veer - who says it's common knowledge that fast ­food chains attract a high number of low ­income earners .

"When you're a low-income earner working 60 hours a week, the McDonald's drive-­through can seem like a relatively cheap and easy option," he said.

"McDonald's franchise owners would know that, and could be charging extra in areas they know are more popular."

Higher-priced items were found in Kaitaia, Linwood, Manurewa, Mangere, Porirua and Invercargill.

Brian McGettigan from Agape Budgeting Services said low income earners in areas such as those were often the targets of big company interests and suffered as a result.

"Well they are often targeted, it's just like fizzy drinks, it does go on, and that just isn't fair for those people," he said.

"We always do try and discourage our people from buying McDonald's; it really is a waste of money."

McDonald's Facebook page has a regular stream of complaints from customers about price variations in McDonald's stores across New Zealand.

"Seriously slack service at McDonald's in Bulls. Not to mention they are more expensive than other stores," posted Natyala Jones.

McDonald's response is that the menu mismatch is down to the individual franchise owners.

McDonald's communication manager Kim Bartlett said about 80 per cent of McDonald's restaurants were franchised. Although the fast food chain set recommended pricing, individual owners set their own.

"Each restaurant has it s own unique costs, services offered and trading patterns so pricing can differ between these," she said.

This story has been amended. A previous version of the story wrongly suggested McDonald's charged higher prices in poor areas, and the article also overstated prices at the Thames and Bombay restaurants.