It might sound reasonable, but that's a very different matter from the purchase actually being an effective per-dollar way to get something that will actually make him happy.

Would knowing that he's commissioned a mega-yacht make me update in favor of the proposition that having a megayacht would make him feel happy or fulfilled? A little bit, sure, it's better than nothing. But I would absolutely weight his thus "revealed" preference less strongly on that question than I would the evidence of simply asking him what he thought about yachts, and even that is pretty shaky evidence.