Nearly a decade ago, I first encountered millennials’ strange fascination with avocados. A younger colleague in Sydney often prepared her office lunch with fresh avocado, spread thick across a slice of bread.

Until then, it had never occurred to me that this was a good use of this odd fruit.

And I felt somewhat sorry for it: my colleague mixed it with an equal amount of Vegemite.

I am not a great fan of either so I cannot tell which was made to taste worse.

What I do know, however, is that avocados have become a cultural phenomenon.

Hardly a week goes by without an avocado related story in the news.

Last year, New Zealand’s avocado shortage made headlines. Prices exceeded $23 per kilogram. Some supermarkets sold them for up to $7.50 – a piece.

Prices have since fallen but demand remains strong, especially among young Kiwis and Australians.

Their taste for the expensive fruit has not gone unnoticed. Commentators wishing to point out how financially hopeless millennials are have an easy time by pointing out their avocado consumption.

Demographer Bernard Salt, for example, had a go at the increased consumption of fancy avocado sandwiches (with or without Vegemite).

As he put it in one of his columns: “I have seen young people order smashed avocado with crumbled feta on five-grain toasted bread at $22 a pop and more. I can afford to eat this for lunch because I am middle aged and have raised my family. But how can young people afford to eat like this? Shouldn’t they be economising by eating at home?”

A millennial might respond that, as a baby-boomer, Salt is having his guacamole and eating it. When he bought his first home, house prices probably did not require cutting back on much. Avocado and feta would not have been a staple dish in the 1970s anyway – and cutting back on them today would hardly yield a deposit on a home.

The latest news from the avocado front comes from New Zealand. Police have warned orchard owners from East Cape down to southern Hawke's Bay to pay attention. Thieves are stealing their expensive fruits and sell them on Facebook.

As an economist, I am puzzled. If avocados are so expensive, why don’t we grow (or import) more? And if houses are so expensive why don’t we build more?

I’ll ponder it over a ham and cheese sandwich.