As a conference organizer for PyCon, I wrote a piece on this last year when the same types of questions arose from a series of Node/JS/Ruby conferences (Non-Profit/Community Python conferences did not, as far as I know, spark the debate).
http://jessenoller.com/2011/05/25/pycon-everybody-pays/
It's a different community/conference and ethos going back the 10 years of PyCon.