Here's an interesting experiment done by indie game developer SoS for Black Friday: he released a bundle of 13 indie games for 1$, available for just one day. He got some traction thanks to Notch, who tweeted that the games were interesting and easily worth 1/13th of a dollar each.

The bundle is (was?) accessible from http://sos.gd/bundle/

The transaction takes place in 3 steps:

  1. download
  2. purchase - this step is optional
  3. play
  unspecified 4: purchase if you haven't, still optional

I personally didn't even download them so I can't say anything about the quality of the product, I just thought it was somewhat relevant to the discussion, since SoS published real time stats during the operation. That's pretty much ideal conditions in my book for indie publishing, so the stats are actually worth something:

4207 downloads and $276 earnings within a single day. 6.5% of the downloaders purchased the product, regardless of whether they liked what they saw.