The taxpayer-funded €2.3m garden was sponsored by Cork City Council and Failte Ireland, to the tune of 17pc and 83pc, respectively.
But on top of these costs, Cork Council has been spending significant sums on storage ahead of the garden's installation there.
Up to last October, €98,000 was splashed out on storing plants and the council has been facing a further amount of €6,000 a month since then.
Work on installing the feature is due to start next month.
The details were contained in the Local Government Audit Service's statutory audit report.
The Sky Garden project has been hit by controversy since it won gold at the Chelsea Flower Show in May 2011.
It had been designed as a 'flying' garden but is now to be installed at ground level in Cork.
It should be hung from a height, but health and safety considerations prevented this.
Since the project was planned, relations between the council and Mr Gavin have deteriorated, with the TV personality calling for it to be scrapped.
Last month, Cork council published its planning application for how the garden will look when it is installed in city's Fitzgerald Park.
But the garden's stand-out feature, a pod hanging from a crane far above ground, will not be allowed.