Not only does it make financial sense - the upgrade-ability and repairability of a custom build in unparalleled by the iMac - esp. the newer one. You would at least need the $169 AppleCare to allow for the possibility of free repairs on the iMac for 3 years. That still leaves out upgrades. Whereas for the custom build it's just a matter of yanking out the failed part and putting in a new one at cost.