technically, the most expensive place to buy a mac is at an apple store or apple.com
many of the catalogs like mac mall, mac warehouse, mac zone and others give you free ram and printers and rebates that apple inc won't give you...and they are well established and generally have as good a track record, or better, than apple inc
i bought my first mac from a friend used and it served us a couple of years, and the mac i am using now is a loaner since he has extra macs at home (like some of you guys here), but i did once buy a new ibook, full list price, from an apple dealer and even though i didn't get a free printer or free ram like the catalogs, i was still extremely happy with the machine and glad i didn't get a pc