Just got back from Pycon - great show.
I've had some time to reflect on how to make conference going affordable, and where my money goes. This year I was partially funded by my employer. I was quite grateful, as I wasn't expecting anything.
What has concerned me in the past is the amount of money put out on travel and hotels. If you're inside the US, Pycon(US) will see the biggest chunk of your money going to the hotel. This is where people (or at least me) say, "Hey, wait a second, all my monetary support for the Open Source Software movement is going to the hotel industry!" Not so fast - actually, although your money doesn't support FOSS directly, it does keep it from *losing* money. To secure a hotel/convention facility for more than 1000 people, there has to be a commitment on rooms. I've seen other devs stay at cheaper hotels for conferences - this is a good approach, if it's done out of necessity. I generally try to stay at the conference hotel in order to support the continued success of the conference - to make sure the conference doesn't lose money.
The travel argument goes roughly the same way - you can't have a conference if people don't show. Even though most of your money is going to the airlines (in the case of Pycon(US) for those outside the United States), your attendance is a plus.