hmmmz, I don't think that's legally defendable in every case, specially when it's an important part of what you buy (Gold Tickets only having a few extras with groupshot being a mayor one)
If an online bicycle store would say "details may vary, this does not qualify you for a refund" and they deliver only a frame instead of the full bike you ordered... They do have that covered in the T&C but it will still be ruled false advertising, see what I mean?
T&C like these would allow Showmasters to, for example, promise guests, shoots, autographs... and then only provide a Halloweenball, call it hallowhedon and keep the money for the tickets.
That's where customer protection laws come in, a canceled guest is bad, but defendable since it's probably not showmasters fault. Advertising a mayor unique selling point (i.e. groupshoot) for a certain ticket (i.e. gold) and knowingly not providing it is not.
What I'm trying to say is that the things T&C can "cover your ass for" (sorry, non-native lacking the vocabulary to say it propperly) is limited by laws protecting costumers from bait & switch (or bait and leave out in this case even) practices.
If you're not going to provide it, you're not allowed to advertise it, the legal and apropriate thing for SM to do here would be to clearly advertise that there was a mistake in putting up the program contents, stating groups shots are NOT included, send out a mailing to everyone who purchased gold to notify them, give refunds where requested and make sure everyone who's assuming it's still part of the program (for example those who read the website before, saved up money and then bought it without re-reading) know the contents have changed from that what was advertised via popup or highlighted text before completing the order.
Not only would that make the whole thing legal and keep them safe from being sued... It would also be a decent thing to do towards the customers (customer=king) and make for a better image of the company
p2p publicity being the most effective kind, specially in close (online fan) comunities.
</ law-geeking out >