I think those data points work together with the "let's think this through for a bit" approach of the article. Particularly, note that the stats that you quoted

I think those data points work together with the "let's think this through for a bit" approach of the article. Particularly, note that the stats that you quoted in your comment are for a 52-week period and include everything that could be considered a "book." I think it's quite logical that 2007's Farmer's Almanac would sell less than 12 copies in the last year, or some vanity-published, typo-laden sci-fi novel of the type my family would sometimes get for me for Christmas (because if it's sold by the Amazon dot Com then it can't be that bad, right?).