Hmmm, can it be that "e" versions are all by default mini-plug now to better suit the iPod mainstream crowd and then a push-on 1/4" adapter is thrown in for the audiophile crowd? The pic below is from the Grado website (specifically, the timeline). This would essentially phase out their mini-to-1/4" adapter, no? (see 2nd pic) And it is certainly cheaper to produce, thereby reducing costs when you compare the two!
VS