It seems to me that national and international meetings are excessive. So much giving is local or regional, and we can network at that level pretty effectively.
It seems to me that people like to travel and this is a good excuse. I also agree very much with Brian that $500-$1000 for a conference is ridiculous. I've organized all-day workshops for $100 per day that easily covered all expenses, and the longer the workshop, the lower your cost per day should be. I know they are often fundaising vehicles, but still!