I am not sure it is the right approach to expect attendees to pay the full price of the per capita conference cost instead of relying on sponsors and donors to cover the majority of the costs.
Having some entry price can serve for creating an interest in the attendee for taking advantage of the conference (after all, they have paid for it, they would not want to waste their own resources), but the overall goal of Wikimania should be to be as inclusive as possible. (The less inclusive it is, the less value it provides to donors, one could argue.)
To achieve inclusivity, I would recommend not setting up barriers that disadvantage groups, by singling them out as receiving subsidies or by setting prices that they cannot hope to pay. (I would also argue that even regional pricing could possibly cause an effect of people feeling like second class attendees.)
We also need to keep in mind, that despite all efforts, it is not possible to come up with a way that can provide support to all potential attendees that require it (scholarships are scarce, subsidies run out); setting unaffordable prices would mean that we would limit the potential attendees to the number of people rich enough who can self select + the hand picked people that are given some form of subsidy (and who knows what group may be left out in the middle).
And finally, we have to consider the function Wikimania serves for many attendees, which is to be able to meet like minded people and socialize (next to learning) - there is a price point where attending Wikimania can be justified as vacation (albeit one that results in contacts and learning that benefit the world), and above which it becomes a "work engagement" (akin to professional academic conferences), however, one where we expect the "employees" to pay.
Best regards,
Bence