If you'll only accept "hard numbers," then you should be asking Paizo themselves what their sales figures are. I'm sure they won't mind sharing them with you.
As for why I think their use of open virality has been good for their company, rather than bad, I suppose we can skip right past the whole "if it was hurting their bottom line, they wouldn't keep doing it (to the point of creating their own license to enable it and then voluntarily publishing under that)" and instead skip right to the correlation between them being one of the biggest and most successful tabletop RPG companies out there while also making 100% of the new rules they make open and viral. It wasn't a coincidence that, during the OGL crisis last year, they were (as far as we know) the company that benefited the most, selling out of months worth of products in weeks. They were also the strongest supporter of the OGL, announcing that they'd fight for it in court if they had to and subsequently their intent to make their own open, viral license.
You don't get to be that successful if, as was declared earlier in the thread, open virality makes it impossible for professional writers to be professionals (i.e. that it undercuts their economic viability).
I think the contention may be just a matter of what is or isn't free game to just reprint when it comes to writing content third party.
Eg, its a pain in the ass to have to tiptoe through the tulips to not accidentally print something you legally can't, when its something like a stat block format or a specific wording.
Granted I'm not a
Its already a meme when would be developers, 3rd party or otherwise, get all anxious about people taking their ideas. Pretty much never happens and even if it did and you had measurable financial harm from it, its still going to be negligible and would be easily sussed out.
