You don't build a billion dollar business to cash out and retire. You would likely end up investing in new businesses and continue from there. In that perspect

You don't build a billion dollar business to cash out and retire. You would likely end up investing in new businesses and continue from there. In that perspective, a billion is exactly a thousand times better than a million. Even more so, perhaps, because it enables you to never have to worry about losing your money and going broke, which you could easily do with a million or even ten.