I don't think this assessment is really accurate. If you're looking for 30 centers, you know what they are, whether they are "starbursted" (like X-Men #100), or not (like Iron Fist #4.)
I suppose to the casual looker who doesn't know better, they might be a bit of purchases based on this, but how much could that really account for?
The 30 centers were tested in 1976, the 35s in 1977, almost exactly a year apart. These details may seem picky, but they are important when trying to deconstruct what happened and how.
Absolutely agreed.
Interesting point to consider: the OPG in the mid 80's noted that X-Men #98 and 99 had a price variant, got it wrong a couple of years ("35 cent cover"), and even pointed out in the Update that they were "NOT RARE!"
Star Wars #1 is the most famous (and long known) price variant, but obviously others were acknowledged long before they became "popular."
What doesn't make sense is this: If Star Wars #1 was known almost from the day it was printed...why did no one make the connection with #2-4, at the very least? Nobody knows.