While this comparison is not exact, it is close and shows that Apple is not always the most expensive. The slight differences are noted.
http://blogs.zdnet.com/Burnette/?p=211&tag=nl.e622
Macworld posted a article a while back that showed that apple is sometimes cheaper. Although it was comparing the Mac Pro with the Dell Precision series
With the Intel transition complete Apple can compete on level ground price wise.
EDIT: Here is the link to the updated macworld price comparison http://www.macworld.com/2006/08/features/macproprice/index.php