And if that's the case then why not pay those who provide the content?
It's interesting to see the amount of support here for doing a TED talk for free when it seems to me most people on HN take a different stance when it comes to doing free design work. In those cases the arguments about getting exposure seem to carry much less weight.
People should be careful not to spite themselves, but at the same time we should not let ourselves be taken advantage of.
Also, I personally enjoy going on stage very much.
Indeed TED events are costly, but TEDx are not, and there are hundreds of them around the world every year. No reason TED global should sponsor them.
Finally, if you're really passionate about something, an 18 minute talk is something you can give away for humanity's sake.