On the contrary, I find that in most jobs I do, there is decreasing marginal utility of my work, since I have a finite amount of energy and the quality of my work goes down as I cross the 40-hour mark. People seem to have individual differences in where this cut-off point is, but I have yet to meet someone who claims it is not there. So for me, given that I value all my work, the concept of increasing marginal utility of work is strange. It would perhaps be different in another field than plain vanilla software development consulting, would be interesting to have a discussion around this.