Code:
http://blog.wolfire.com/2010/05/Saving-a-penny----pirating-the-Humble-Indie-Bundle
This is for a game, so the demographic will be different. They basically let consumers decide how much they wanted to pay for it, with a minimum price of one penny.
So far it has been downloaded 80,000 times, and generated $683,000 which gives an average of about $8.50 per download. But 25% of the downloads were unauthorised, and came from links posted on pirate sites, so the real average payment would be much higher.
The 25% who wouldn't even pay one penny for it suggests that their piracy is not financially motivated. The blog post gives a few suggestions for what their motivation might be, and they all seem reasonable enough to me.
Though the obvious one seems to be missing -- most people downloading it for free won't know that they could have bought it legally so cheaply.