Yes, it's principally the same driver in terms of weight, impedance, and magnet size. But just like their phono cartridges, these drivers are "binned" and the ones that are furthest away from the RS-1 become SR-60's and so on and so on.
It's the same thing they do with computer CPU's and led's, the highest binned ones are sold at a premium, and the lower binned ones become lower end more affordable products.
So while yes if you simply imply that they all use the same driver, of course it would sound absolutely ridiculous for someone to pay for the same driver in a 700 dollar top of the line reference series headphone, but a modded headphone will only get close at the most absolute best case scenario, but the heart of the headphone I feel never really quite measures up. My SR-60's are more exciting than say a stock SR-225 because of the bass holes, recable, and headband, but an SR-225 doesn't need any of those things to sound good, the bass sounds deeper because the driver is physically capable of thump, versus porting your driver and artificially enhancing it, and you'll know, when your mids start becoming a little muddier at the expensive of all around great bass.
I can't speak on cables, but I recabled my own headphones with the help of other people years before I ever did it for anybody else, and I'm still one of the biggest consumers of my own stuff hehe.
My beater 4 year old SR-225 with 7N silver cable, leather headband, no bass holes. They sound more interesting than the RS-2's for sure, but one is an RS-2 and has wood, while one doesn't hehe. I'd mod the RS-2 if I wasn't looking to sell it, or if you didn't have to spend 75 bucks to send it back to Grado to install the cable for you using their special oven... ouchies.