Employees who freely take the best option available to them are not made better off if that option is removed.

I don't believe that Bezos or other employers are acting selfishly when them employ people, even when they make a margin on that labor. (In fact, if they don't make a margin on that labor, they would be better off to stop employing that person, meaning the situation where the employee and employer both make money on the deal is the most stable state.)