I have been to several of these conferences in NYC and San Jose. I does cost a big buck. While I am there I write down lots of ideas and when I come home I usually have an "attack list". A few months later I can look at the attack list and tally up how much I know that those ideas have yielded. It is always worth more than the price of the meeting and expenses.
One idea can yield the cost of the registration fee per month - and there you have fantastic ROI.
I used to work at a government agency and the director said... "The most valuable asset of an organization is the accumulated knowledge of its professional staff". Tell that to your boss.
Finally, at these meetings I have met many of the people who post in the forums and now we are good friends. I can email them with a question or call them by phone - and that advice can be invaluable.
* "It's not the size of the dog in the fight that matters, it's the size of the fight in the dog." Mark Twain
* "Free advice isn't worth much. Cheap advice is worth even less." EGOL