It wasn't planned to the detail but the concept was simple. Integrate an orthodox Budget with measures of wellbeing, develop a new wellbeing criteria against which new funding must measure up, and voila.
It has been a marketing triumph for Ardern and Robertson so far.
The fact that the shamefully neglected area of mental health has been the centrepiece of the first such Budget and that it is the first Budget to contain a progress report on child poverty reduction has cemented the concept.
It is so simple that it's a wonder it hasn't been done before – although it has in bits and pieces.
Previous governments have set targets, measured progress and funded programmes on the basis of evidence that they work.
They had their own marketing and presentational packages for them, social investment and better public services.
But they were not promoted as being at the heart of the Budget.
Environmental monitoring, for example, required under the Environmental Reporting Act 2015, measures nine factors such as water and air quality but are reported under the Budget.
The Wellbeing Budget is not cosmetic but it is not revolutionary either.
National leader Simon Bridges claims it is style over substance.
But it is both style and substance.
A lot of it is about emphasis and that "wellbeing" word.
But when you are allocating almost $2 billion to mental health and indexing social welfare benefits to the average wage, it is also about substance.
The feel-good factor about the 2019 Budget is mostly about where it has directed its new spending.
But the level of spending is not likely to be sustainable, especially if revenue forecasts turn out to be heroic in the face of slowing growth and GDP.
Robertson says Wellbeing Budget means using indicators other than GDP to measure success.
Some of those measures are empirical and perfectly reasonable. Others are daft and open to mockery.
For as long as the economy is growing, a Wellbeing Budget will be a perfectly acceptable and welcome way to present a Budget.
But the moment the economy turns south, the feel-good factor may not last.