From the FAQ:
Q: Why is your event so expensive?
A: Well, it’s a massive, history-making event. That means a lot of staff, infrastructure, and expenses. Not to mention insurance. (Don’t get us started on that topic!) We’ve also spent more than two years planning this magnificent event for you to enjoy. We’ve done our very best to solicit as many sponsors as possible and include as many features as we possibly can along the way so that we can increase the value of your participation while keeping the costs as low as possible.