You don't need to wonder or make changes to "fix" this problem. If Amazon or anyone was making $5000 off employees they paid $1000, they would hire more and wages would go up.
That assumes that there is no diminishing return on additional hires. If I run a warehouse that generates $100,000/mo with 10 employees being paid $1000/mo and those 10 employees satisfy the needs of the warehouse, I wouldn't hire more for fun.
There is some finite amount of demand that needs to be processed by the warehouse, the fact that I can satisfy that demand with a small number of low paid workers doesn't somehow increase the demand.
