As soon as you charge and accept money in exchange for a service, you have a responsibility to provide that service. Not doing so is a dick move.
Such a simple concept yet some don't get it because they thing their discussion is more important than a humans word.
Ah, the old standby "breaching a contract is bad". But there is a whole line of economic reasoning - revolving around economic utility - that we WANT parties to breach when it makes economic sense to do so. Since the fundamental remedy for a breach of contract is "putting the parties in the same position they would have been had the contract been performed", we WANT parties to breach if the effort - the "utility" of performing the contract - far exceeds the utility of putting the party in the position they would have been. We have a value for the tickets; it's the purchase price. If certain members of the audience have extraordinary values placed on the concert, that's not something that, from a utilitarian perspective - we want the Eric Church's of the world worrying about. It's economically wasteful.
So, XJ is wrong; if you charge and accept money for a service, you have to provide something in kind that is of equal value for that service. The intangible "worth" of the experience is meaningless in this discussion. He refunded the ticket prices; he has fulfilled his end of the bargain. The people attending that concert were put in the position they would have been in had the concert been performed.
Now, we can debate the moral side of this, but morals are a subjective thing, and while I disagree with Ben, some of the responses I feel are being overly harsh. He's entitled to his view on this (a view that I empathize with, even if I don't hold it myself).