I can't see a table like what's in the article without poking at it some more in Excel. Anyway, as you go down the table, the increasing cores do indeed have a higher cores*GHz. If you look at dollars per core-GHz (yes, I recognize this is silly), you get a generally increasing trend as you go down the table, but the E5-1680 is $63.35 per core-GHz and the E5-2680 is only $60.59 per core-GHz.