I too agree that the fact that the mean can be strongly influenced by abnormally large (small) values implies comparing the *average* price paid is not that meaningful. As the previous poster commented, the *median* is a much more meaningful statistic in cases such as this.
Based on this reasoning, I emailed the Humble Bundle support team asking whether they could calculate the median on the numbers. They just answered:
"During a bundle we're usually far too busy to work with the data in real time, but we usually release a data analysis after we're done. So, hang in there or take a look around at previous information we've released such as this speech:
http://www.gdcvault.com/play/1014437/The-Humble-Indie
Thank you for your continued support"
So it seems we'll have to wait until the Bundle is over (not much left now) and they tally and analyse the results. I still predict the Linux median will be the highest.
Just out of mathematical curiosity: is it possible to estimate the median for each group somehow, based on the information available (average for each group, numbers in each group, total amount paid by all groups)?