I don't think you can capture the complexity of the world with a single variable. I'm at Amazon. We all make about the same. Some more than me. Some less. However, while I don't have to worry about changing jobs, or _not_ having a job (for awhile), they do. They're working with an entirely different set of pressures and constraints.
For me, I can hop ship, decide I don't like it, boomerang back or take some time off no worse for the wear. That level of autonomy doesn't exist when you've got 60 days to land a job or uproot the life you've been building. Salary is a minor part of the picture. If changing jobs is a gamble that might end in "leave the country," the employer gets a certain kind of "loyalty" that salary cannot buy.
For me, I can hop ship, decide I don't like it, boomerang back or take some time off no worse for the wear. That level of autonomy doesn't exist when you've got 60 days to land a job or uproot the life you've been building. Salary is a minor part of the picture. If changing jobs is a gamble that might end in "leave the country," the employer gets a certain kind of "loyalty" that salary cannot buy.