Ask HN: Should you pay to present at an event?

Awhile ago I posted this thread about David Rose and Why NY Angels (his organization) Charges Entrepreneurs http://news.ycombinator.com/item?id=1155973

Since then I've been approached my many conferences (DEMO, TechCrunch Disrupt, NY Venture Summit, etc) who charge to present and their reasoning behind doing so.

I totally understand that it costs a lot of money to put on a conference (to reserve the space, logistics, food, etc) and the organizer should be compensated for their time. But how do you feel about paying to present at an event? Especially an event like DEMO which charges $18,500 just to present?