And Amazon's margins are far smaller than you're implying. Their latest quarterly had a profit margin of 0.59%. They have more than half a million employees and a net income of just ~$2.4 billion. Imagine they give a modest $1000 raise to all their employees. That'd be more than $500 million or about 23% of their entire net income. Mass increases in labor to the point that the hourly requirements of each employee substantially decreased is simply out of the question.
In looking at wealth inequality, I think we lose track of how many of us there are. If you received just $1 from each person on Earth you'd be the 175th richest person in the world. $15 per person and you'd be, by far, the richest person alive. And that also goes the other way - even the richest are diluted to very little on the scale of the populations of this place we live in. If every single dollar or produced value, at least according to GDP, was perfectly evently distributed in the US we'd each get about $52k a year. Getting about half the average for moving boxes doesn't seem like something that screams catastrophe to me.