Great question Kelley. Without providing a full audit, it covers the costs of maps and t-shirts for everyone, name badges, and other minor misc. things. This year, the registration covered everything within 20 cents or so of the actual costs. Throw in the fact I got extra maps and t-shirts for "just in case" that didn't happen, and I ended up in the hole. :-/
Bottom line: nobody is making any money off the registration fee, if that's the concern.