If you think about a economy it has some amount of productive capacity. You can sort of use GDP to see it, but that is denominated in dollars so it can hide the effect to a large degree. When people shift to alternative goods, productive capacity can shift to producing those new goods, however if the total capacity remains the same those dollars still purchase less productive effort than they did previously. As dollars are the reward for productive effort in the economy, if your wages remain the same your proportion of the efforts of the economy has gotten smaller, but your contributions remained static. I imagine this has contributed to income inequality to some degree.