To Scott Briefer's point, your assertion would be correct if indeed it was the SPIDERMAN producers who were holding on to the money.
Unfortunately, the producers do not take possession of any of the ticket sales revenue until the performance is played. Telecharge and Ticketmaster remit the money to the theatre owner and the theatre owner gets the benefit of the interest on the advance sales -- not the show. There is the occasional show that is able to negotiate a piece of that interest but those are very few and far between.
The producers of SPIDERMAN therefore have absolutely nothing gain by not authorizing a refund of monies paid for performances that clearly will not happen -- except perhaps to create an even bigger public relations debacle.
"No matter how much you want the part, never let 'em see you sweat." -- Old Dry Idea commercial