This card shows the price of a Vietnamese banh mi pork roll

Not all banh mi are created equal. Toppings can vary from charcuterie, to crackling roasted pork belly, to Chinese char siu barbecue pork.

Mr Mallis said he tried to standardize prices by looking for any menu item that said ‘crispy pork’ or ‘roast pork’.

“It’s the one I’ve seen in almost every banh mi store I’ve been to and I think it will be a good reference,” he said.

The price index runs into trouble in the suburbs which are relative banh mi deserts, as the average cost is dictated by one or two data points.

“If you look at Hobsons Bay, for example, that comes out as the most expensive council area. But it only has, I think, three or four stores and there are one or two that are at the high end of the price range,” he said.

It’s not the best place for banh mi cheapskates, but the easiest place to find a roast pork roll is Melbourne’s CBD.

Mr Mallis said there are around 70 shops selling banh mi in the city center but he is adding more establishments to the citywide map as people share their locals.

While useful for those looking for a cheap lunch, the card can also be seen as a way to keep up with gentrification in Melbourne. A banh mi costs $1 more in Northcote than in Preston, for example.

Chef Jerry Mai said the average price for a banh mi is much lower than it should be, considering what you get for the money.

“When you walk into a sandwich shop and buy a roll of roast beef, it’s a $12 to $13 deal and I don’t bat an eyelid,” she said. “Over $6-7 for a banh mi, people seem to think that’s the price – maybe 10 years ago.”

Comparing the prices of a Melbourne bakery to a street cart in Saigon was not a useful comparison, Ms Mai said, because of the difference in cost of ingredients, rent and wages.

She also said the Australian version was often overfilled: “the number one feature is the roll, the crispy crust, the soft inside”.

When it comes to the more sophisticated types of banh mi that appear on menus across the city, it’s important to remember the dish’s simple roots.

“A banh mi is a working food that we grab, eat and leave,” she said.

“It’s not about filling it to the max and putting caviar in it. We just got a little carried away.

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