Parmandur
Book-Friend
Well, I was thinking "no Beyond" and "not a huge percentage would be Amazon, or Amazon may have been better st reporting 20 hears ago". But you are right, FLGS would still be a big driver for the numbers to be below the 75% normally accounted for by Bookscan.I doubt that bookscan would represent a higher percentage of 3e sales than it does 5e sales. FLGSes don't report to bookscan - and certainly didn't then - and I'd expect that with 3e, the VAST majority of its sales were still from hobby stores and the like.
Still, though, the relative 3E numbers versus 5E numbers are drastic based on what was in that data. Several 5E supplemets have sold more on Bookscan than the 3E PHB did.