I believe that the specifications and pricing for all of the non-Retina iMacs stayed the same. The addition of a Retina iMac was the change.
With the Mac Minis, there were price cuts and specification changes, though some of those changes (no more user-upgradable RAM, no more quad-core CPUs on...
$700 more than the 3.2 GHz model. But looking at the 'off-the-shelf' 27-inch iMacs, the 3.4 GHz quad-core Core i5 model has a somewhat closer CPU/GPU specification match to the Retina iMac. That model is $1999, hence $500 difference.
It may cost a bit more than a regular 27" iMac, but for $500, you get a Retina Display, an upgraded GPU, and an upgrade to a Fusion Drive. Meanwhile, a Dell monitor with the same resolution as the $2499 Retina iMac goes for, you guessed it, $2499 … for just the monitor.