Remember what we said a little earlier on about all the real money being in tech companies? This might be an even better example than Bill Gates and Larry Page ('Larry' is obviously a great name for tech billionaires. Remember that when you're naming your children). Larry Ellison founded Oracle, which is a software company so enormous that only Microsoft have then beaten for size or net worth. With all the money it generates, Ellison has found the income to buy the Hawaiian island of Lanai for somewhere between five hundred and six hundred million dollars.
It's easily the most expensive island on our list, but Ellison isn't even going to live there; he's turning it into a state-of-the-art tourist resort! Given that we've seen other celebrities charging up to $30,000 per night to stay on islands that cost less than a tenth as much as Lanai, we shudder to think what a night on Lanai may cost visitors in a few years' time.