I wouldn't say that's the obvious conclusion, if only because it assumes that income is highly enough correlated with work effort.
It doesn't strike me that such a correlation, which I do believe exists, is obviously within 20%, for example.
Moreover, I would consider the situation of working at or very near capacity and yet still not producing to be a plausible, if not likely, source of feelings of futility.
Some commenters wonder why high income rat-racers don't attempt suicide, then learn to stop and smell the roses, and lose income. I doubt that this is common. Suicidal feelings are brought on by a sense of futility, not stress or overwork.