I’m actually surprised this has been highlighted as a new issue: for as long as I’ve worked around the Mac market, Apple has been renowned as a relatively low-payer. Its salaries are competitive, but towards the lower end of the mark.
How does it get away with this? Mainly because lots of people want to work for it – simple supply (in this case of eager engineers) and demand.
I also find it pretty interesting that people are more interested in the salaries of engineers, while not giving two hoots about the salaries of the factory workers who actually build the products (and who won’t be getting any options any time soon).