Indeed very interesting. It is a fundamental principle of finance: Investors seek to maximize utility, but this is under the axiom of complete rationality. And even if that condition is met (which I doubt), the utility function of money is not concave at all levels, for example leftmost of the graph, before the price of food. I think that after some point, utility becomes flat and Musk is way beyond that point. Additionally he seems to be a risk loving investor, not a risk averse.