Yep, given the nature of the problem, I'm not sure a clear scientific study could be made, and in lieu of clear facts, just how much digital piracy hurts actual sales will be debated in circles.
It's common sense that in a lawsuit WotC will argue the worst case scenario and that every view and download was a potential lost sale. It's pretty safe to assume that no, not every single one is a lost sale. However, the other extreme of "all piracy is actually good because it acts like a preview for people to actually buy the books" is also pretty safe to assume is false, especially for a very well known market leader like WotC or even the "everyone who downloaded it would never have bought it anyway" is probably not 100% true - not to mention contradictory to the previous view of illegal PDFs being good previews.
However, as to which end of that 3 pointed spectrum the truth lies (downloads = lost sales, downloads = increased sales, downloads = irrelevant) is utterly unknown to anyone, and probably varies a whole freakin lot between companies and even products at a single company.
So, yeah, it's doubtful that the harm is as bad as WotC argues (although, again, it's sensible in a lawsuit for them to argue worst case scenario and the judge to balance the two sides) but it's also doubtful no harm occured. But all anyone has are guesses as to how harmful it really is. Which is a shame, because some actual facts would be nice in these sorts of discussions, but with so much variation and such difficulty in accurately tracking these things, we'll be stuck with anecdotal evidence and competing philosophical agendas for a very long time.
I understand you completely, it's just that when studies have been done on these subjects, they often really don't support many of the arguments made.
I buy books from WotC because I like their products, I think they are worth buying, and I want to do my fair share in keeping the company profitable and alive. I personally believe that any person who can afford to buy from WotC, claims to like the product, and chooses to pirate instead is a selfish shmuck, but that's just my opinion.
I'm just sharing my experience, and just for the fact that *I* exist, with the habits that I've already described, means that obviously the rule that a pirated copy = a lost sale is not true, and I find it a pretty unlikely possibility that I'm the only person who falls into such a category. How much it's not true is a matter of complete conjecture, but my gut feeling is that the loss is vastly overestimated, but it's impossible to prove or disprove.
I certainly concede that not everyone is like me... because I would haven't of put the files online for everyone else to get in the first place. Just for that fact, there obviously aren't like me.