Yeah, that's the point. Legality and the sale price of $5 are the distinguishing features, not the fact that it was potentially available for free, as the article implies. It would have been available for free regardless, just as all of the other albums on that list are. From the consumer's perspective, downloading over a file-sharing network is the same whether it's legal or illegal. Making it legal to share it that way does not induce significantly more people to do so (some, yes, but not many); it only means the people who would have anyway are not infringing.

So I think that factor is less significant than the sale price of $5, which does induce more people to buy it than a higher price would.