I think the OP just means productiveness in time, ie. spending 8-10 hours a day moving product while being paid 2x but working 3x as hard isn't as 'productive' as if you were doing something you loved for those 8-10 working hours, even if you were being paid a median $7.50/hr wage (not that most would achieve this by working the gas station register). If everyone could get a free education in what they want to do for a living, people wouldn't choose to work at Amazon and waste a third of their daily life moving boxes.

The root of the problem is that Amazon's $15/hr minimum attracts talent as a result of the price of things, including rent, continuing to rise, sometimes up to 15% YOY - people are often required to either work 16 hours a day at 2 jobs or work 8-10 hours at Amazon to reach the minimum income needed to have nice-enough living conditions.