Offering to let your customers pay what they want seems to be a recipe for disaster, but counterintuitive as it sounds, it actually works.
Case in point: I purchased for the current iteration of the Humble Indie Bundle, featuring games from Frozenbyte. I also bit the first two times, paying just $5 for packs of four or five games from independent developers.
Why does this work out for the developers? Speaking from my own psychology as a (somewhat miserly) buyer, I would never have bought these games in the first place for whatever price they might have been asking. But by offering it at as a time-limited sale, the compulsion just becomes all the more irresistible.
But the real value they're getting from me isn't even in the $5 I paid. Rather, it's in my attention. If they hadn't offered this as a pay-what-you-want deal, I wouldn't have heard of them. In effect, it accounts as advertising; and while it doesn't guarantee I'll be buying from them again, it at least opens up the glimmer of a chance that I will in the future.