Just my two cents on ticket prices for Wikimedia conferences:
* I can confirm with what has been said about other, professional conferences. Note the term "professional".
* Having a voluntarily higher price for supportive participants is something we could try. We could even try to distinguish between Wikimedians (a broader definition than scholarship recipients, eg. connected to the voting rights which already define reasonable criteria) and "outsiders".
My personal experience with setting prices for Wikimedia conferences: Concerning WikiCon 2012 we were thinking it from the perspective of the attendee. We wanted to get people who are not Wikimedians to attend as well. So we offered day tickets and set their price according to what we thought would be the max of what somebody who doesn't exactly know what to expect and is just curious would be willing to pay. In that case we came up with 5 EUR, a price level comparable to a visit of a mid-level museum or a disco. The price for the whole conference was then interpolated from that.
So the question is: What is our target group and what makes sense to them to pay? * again, splitting between Wikimedians and non-Wikimedians came to my mind (how does the LinuxConf.au distinguish whether one is hobbyist or professional)? * I agree with what has been said on volunteers not willing to have to pay for their hobby, if they already contribute so much else, no matter what they actually earn.
/Manuel