It depends a bit on what you want for skirting and steps but generally raised decks are not substantially more money than decks at or just above grade with the same surface area and materials. Their biggest virtue is that they can make future repairs a bit easier but here in North America I am perpetually trying to talk my clients out of raised decks (they are enormously popular here). In my design practice I try to integrate the garden with views from within the house; reasoning, in part, that within the house is where the clients actually spend the bulk of their time. A raised deck of any size pushes the view from within too far out into the property and ruins the integration of house and garden that I'm after. They can also be difficult to effectively integrate with the architecture of the home. Higher decks also create rather difficult spaces beneath them. In the U.S. it not uncommon to see decks two or more meters above grade.