You assume that all of those downloading from the torrents have not paid or will not pay. I have heard numerous reports of people who have paid, been sent a link and been unable to download from the official site due to congestion, and I'd bet a number of these will go to the torrents. Additionally, there are a number of people who refuse to pay before they are permitted to try a product.
I have paid for the $5 version of this (and will download it when I get home) but I refuse to buy new music at high street prices without hearing it first, so I download it. If I don't like it, I delete it from my machine. If I do like it, I go out and buy it. I don't see why people would behave any differently in this case. I chose to pay the $5 to get the music without hearing it in this case because I applaud the model and want to encourage it, but that will not be the case for everyone.
I'm sure there are some people who will download and listen to this music for free just because they can, but I'd be very surprised if they were the majority. The fact is, we can't tell - just because they are on the torrents does not mean everyone is automatically depriving NIN of sales.