And I disagree.
Let's say you were travelling somewhere by air, and you have to make a connection. You get to your midpoint, and the airline tells you your next flight has been cancelled. They will (in the goodness of their hearts, because they're such a *caring* company) refund your money. However, they have rescheduled a new flight 15 minutes after your old one. And hey! They'll let you have an equal chance with all the other customers to book onto it (move fast, though, it's going quickly), and it'll only be, oh, five hundred dollars more than the flight you originally booked. Perfectly fair, right? You'd be perfectly happy with that?
Seriously, what the OP describes is not a "new" concert. It is a rescheduled one. If you can't see the difference, fine, but the OP has every right to write a letter of complaint, just as the brokers have a right to ignore it if they wish to.