It will be expensive at first but long-term, the social, economic, and environmental benefits could be enormous. It's not just about one little island.
Socially, the idea isn't so much to promote one particular ideology, but to allow experimentation with lots of different economic and governmental structures, in an environment where people can easily move to the ones that work the best. The book points out that similar conditions brought us the advances of ancient Greece and renaissance Italy.
Aquaculture on the open seas looks very attractive; the economics work out well and it's great for the environment. And small island nations with good access to shipping and lots of economic freedom have tended to do very well in general.