Oscar Wilde warned against knowing the price of everything, but the value of nothing. This week we've seen the government realise the value of milk and opt to find out the price, while adidas know the price of a rugby jersey, but not the value...

And so the government has come around, and announced a select committee inquiry into the price of milk. It's a U-turn (or should that be moo-turn?) for National given its confidence at the start of the year that no such inquiry was needed.

It was clear such a backdown was imminent when Agriculture David Carter went on Q+A on Sunday and said he saw "some value" in an inquiry, for which Labour, the Greens and Consumer New Zealand have long been agitating. John Key says the select committee will be given wide powers.

That's a far cry from February, when Carter was reported saying that such an inquiry was unnecessary, given the three ministries investigation already underway and due to report before the end of the year:

"Let's wait and get the report that I've called for, which at least will give us some indication as to how the competitive market is working," he said.

Six months later, however, there's no more time to waste. Why? The election, of course. National has a comfortable poll lead, but one of the places it remains exposed is the cost of living.

As Food and Grocery Council Chief Executive and former National MP Katherine Rich has said, her organisation's polling shows that food prices are on of the public's top concerns. On such hip-pocket issues are elections fought.

On National's watch, food, petrol, power and rates bills have gone up and up. Voters have been very patient with the government, tending to blame the global recession and being inclined to like John Key. But voter patience is always finite. That's why three out of every ten words Labour leader Phil Goff says are "cost of living".

So what does the select committee need to do?

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