First, all conferences are expensive in terms of time and money. That's a given.

> just to watch Zuckerberg reveal something I won't use

I think you're overlooking the value. It's not about going for a keynote or being entertained/catered to; its about the interaction. The ability to talk to the people that've built the tools you are using is extremely powerful. Would you rather talk to an expert on a subject matter, or post a question on SO and hope someone has had a similar experience? This is just one of the reasons why conferences like this are "worth it".