If you honestly believe that they're the same drivers throughout the range you're so incredibly uninformed it's almost offensive. Not only are the drivers different but most of the enclosures are different as well. Very specific breeds of mahogany trees are picked for their RS-1 series and the size and dimmensions are very carefully designed.
Look it up. All modern Grados use the exact same driver. The enclosure is what's different between the models.
I hate that this is going way off topic, but:
care to tell us where to look it up?
I've read the rumours in several places including this forum, but have yet seen no actual irrefutable evidence to support this bold statement.