So your choice might be this: a mighty big deposit on a house in Grammar zone, or a child until the age of 18.

Put that way, raising a child until the age of 18 years and only spending $250,000 seems relatively cheap - just one quarter (roughly) of a very expensive asset, paid over almost two decades.

The calculation of $250,000 has been included in a draft study for the Inland Revenue Department, and we'll see in two weeks or so how it has been used in a Government review of the formula for determining child-support payments.

But of course, no-one in their right mind believes $250,000 for 18 years is remotely accurate. How can it be, especially in places like Auckland? For one thing, if you have children, you are often driven by zoning into more expensive areas. So is almost everyone else, with the consequence that you are paying hugely inflated house prices, rates and associated taxes.

But that isn't the real reason this estimate seems so far off base. The problem is that it does not factor in the cost of childcare - which a majority of parents use - or factor in the lost income of one parent staying at home to raise a child.

Most parents I have asked pay between $50 - $75 a day in childcare costs. Even at the lower end that could represent a figure of $250 a week, or some $13,000 a year.

Interestingly, US authorities give roughly the same total figure for the average cost of raising American kids - some $290,000 now ($250,000 a few years back). But this is also without childcare, which US parents use even more frequently, and start using much earlier on (as they have no federally mandated paid parental leave).

Just like anywhere the cost of childcare varies, but in the US you'd be lucky to pay less than $20,000 a year.

The cost of one person not working is big, and even then there are few parents who could avoid sending their kids somewhere, even if it's for a few hours a week. Public kindies are free but usually not available until closer to four years of age (around my neck of the woods, anyhow). That leaves private kindies which, even with the Government's 20 free hours scheme, still charge up to $20 for a session.

Then there are the school fees, activity costs ... and the overarching costs of even the cheapest forms of fun and entertainment.

Of course it could also be argued that two people living together without kids would spend the same amount of money, except they would spend on fun things like holidays and dinners out and shoes. Parents living frugally could arguably spend much less (though realistically to have any time out takes some measure of money, and those who say otherwise are dreaming!)

And of course the old chestnut always gets trotted out - that children should not be accounted for like power, water and electricity. Indeed, our parents, who never seemed to have the luxuries of life we enjoy, didn't appear to have all the soul searching about how many children they could afford and why.

But we do live in a different world now, where even free education has costs attached, where relatives and friends have less time to give over for child-rearing duties, where doing right by your children often equates to spending money (and we're not talk here about purely indulgent toys and trips away).

It may be a bit sad to do the sums on having children. They are (one hopes!) an asset that will pay dividends for years to come. But the reality is that no gain without pain - and this particular pain is one that will hit your back pocket with some force!

Photo: Even free education has costs attached. Photo / Greg Bowker