Workers' Party councillor Ted Tynan said the council needed to clarify precisely how much the garden cost, and what extra money the council would pay in transport, insurance and operating costs.
Ted also expressed disbelief that the garden -- including its 30-metre high floating 'pod' and crane -- may only open for three months each year.
"I love gardens and flowers and parks, but this is absolutely ridiculous. You'd put a hell of a lot of flower beds around the city for this kind of money. We should keep our feet on the ground not in the clouds with a sky garden'," Mr Tynan said.
"There are 500 boarded-up council houses in Cork and 120 people with various disabilities waiting on home adaptations. But the funding to do to all this has been cut by central government. We must seriously question the Council's priorities when this sort of thing is taking place," he added.