Amazon pays $20/hour because most people don't have the mental constitution to put up with it. It's pretty dull.

When I was hired as a part-timer (no interview!) at a warehouse there were about a dozen of us. In a month maybe four were left. It wasn't terribly physically difficult, though I was fairly sore. But there was nothing good about the work.

It was just repetitive, isolated tasks where you have to consciously decide not to meet the unrealistic standard, or just blindly follow the orders on the device, or guess how fast to work to avoid a strain injury while not being obviously slow.

To give some examples, we'd take bags (totes) from specific locations as indicated on our device, pack them on a large push-cart, and shuttle them halfway across the warehouse. Or we'd pick packages for a specific location off a conveyer belt (which usually moved too fast). Or we'd spend 5+ hours, alone, unfolding bags and putting them back onto the shelves.

There's probably some analogy to be made with software development here, based on what I've heard, but I'm only a CS student.