I wonder if indeed it's completely out of any state's control or it's technically still in a state's jurisdiction. I wonder what would happen if someone bought an island and started hiring people and making money there and not paying any taxes. My guess is that government agents would suddenly become very interested in that piece of land and would pay a visit.
I'm not sure I understand why being an island is different from any other land. It's still under the tax jurisdiction of the Province and Country. How is this different when I replace the word island with acreage or farm?
I think this answers the question of "but if you don't like the rules, you can always leave". In fact, you can't. Even if you can afford a piece of land like this, you're still a subject of taxation of some country.