Small claims court is useful. They either have to pay up or show up in court, to start with. Paying up is usually cheaper. Not showing up means instant judgement for the party that shows up.
Or just do a credit card chargeback.
Ya but I wouldn't be surprised if the Ticketmaster TOS that you sign (click) makes you give up your suing rights in favor of arbitration or worse.
Actually I hope they do, because an arbitration DDOS will cause them much more pain than a case action.
Then everyone affected should file for an arbitration.