Do billionaire investors sometimes opt to press the proverbial easy button? You bet they do. Making money the easy way is preferable to doing it the hard way regardless of how much money you have. The easy way of making money to which I'm referring is investing in exchange-traded funds (ETFs). With ETFs, you can buy a basket of stocks without spending the effort to research each stock. Warren Buffett and Ken Griffin stand out as two of the most prominent billionaire investors on the planet. Buffett has led Berkshire Hathaway to reach a market cap of over $850 billion.