It's not really about SD cards, per se. It's about having adequate local storage. So, the rebuttal to this is really simple. We are the 1%. If your statement is true, then 99% of the 30M GS3s that have been sold would have still been sold, even if the GS3 did not have more than 16GB of storage and did not have a swappable battery. Roughly, that still works out to 30M phones.
And I think that is a fantasy, and for 2 reasons: One, a bunch of that 30M would not have bought it, because it was limited to 16GB max, or because you can't swap the battery (or both). And, two, another big pile (the even less tech-savvy) would not have bought them because when they read ANY reviews or consumer reports they would not have said "the Samsung GS3 is the clear winner." Instead, they would have read reports that said "the HTC One X is the pretty clear winner here." We can never know how it really would have played out, but you'll never convince me that a GS3 with 16gig max and no swappable battery would have still sold anywhere near 30M phones in the sameness amount of time that it did.