Happiness is the function being maximized, whereas money is just one of several parameters/variables in the equation. It's an important distinction. You can't treat them as two parameters being maximized - for a few rare people, for example, the two are completely inversely related.

But why both? I'm not interested in pissing contests over who has the biggest number. What good does more money do me, if it costs me happiness?

Money is insurance against future unhappiness. Bad things happen for no reason, and you might need money later.