Well, consider this. There were clients involved. It's almost likely these clients paid Clear Channel to get in on the promotion, and to have announcements made on-air. As I read elsewhere, CC was trying to sell booths at their event for less than ToS was asking... in effect, CC was trying to undercut Galaxy.
Since the event didn't happen, these clients now have to be refunded. Joel gets to explain to corporate why he needs to issue refunds and/or why he's going to have to sacrifice a boatload of otherwise saleable airtime to make room for makegoods. Of course, as in any other desperate make-good situation, they'll probably just add the makegoods to the existing spotloads, rather than replacing other spots. In the end, CC tries to cheat Galaxy, but CC's listeners are the ones who get cheated. Unless CC winds up cheating itself because listeners get upset with longer stopsets and turn the dial elsewhere... except for the fact that CC's biggest cash cow happens to be the one format that has no competition in the market.