If you up 3.4 i5 27" iMac to the fusion drive with which the i5 Retina iMac comes standard with then there is only a $300 difference between them. Upping the processors to the respective i7 upgrade the result is much better for the Retina iMac with regards to price/performance from early speed tests results that have been posted. Additional upgrading of memory, storage and GPU are similarly priced. So it looks like even if your not going to do a lot with 5K and also use it in lower resolutions which still have a pixel density advantage, the Retina iMac is a very good value. The only advantage for the standard iMac is the ability to be used as a display for another Mac using target display mode via thunderbolt. Of course the Retina iMac will need some use and testing before this concussion can be confirmed.