Interesting that the numbers varied so much. My thought being that this is an example of how "de-valued" apps are in some people's minds.
Lead developer, Craig Hockenberry, finally got a chance to post his answer (see [1] for his reply and then [2] and [3] for the back story) and his numbers were far different than the original best guess. Another (non-Icon Factory developer) answered and his were more in line, but based on experience.
[1] http://twitter.com/chockenberry/status/27263467482
[2] http://twitter.com/chockenberry/status/27258821176
[3] http://twitter.com/chockenberry/status/27256591312