Earlier quoted context omitted.
The whole reason why warehouse workers are paid so little is because just about anyone can be trained to do it. It's simple economics. You are kind of right about subsidizing workers, but that's more of the government's fault for how our social services benefits work. It's not Amazon's fault the going rate for labor is below the rate that the government will provide benefits for.
Since when is "economical" equivalent to "good"? The whole reason children work in coal mines is that others can't fit down the holes, it's simple economics. The reason black slaves work the fields is because white folks don't want to do the work for the going rate, it's simple economics. Economic forces are not guaranteed to produce a just society.
Your other two examples are quite the jump though, and not really worth commenting on.