As for remedies, see my post above. The usual measure of damages in contract is expectation, not restitution. Breach of contract claims deal with "hypothetical things that never happened" all the time, that's required by the very nature of expectancy damages. And in any event this is an easy case as the FMV of the tickets at the time of breach is easy to calculate.
This is just like selling 100 shares of AAPL and then before T+3 happens deciding you aren't going to honor the sale because the price has since gone up. You aren't going to get away with just canceling the sale and returning the money.
Edit: You don't seem to understand that damages, legally speaking, include not getting something valuable just as much as it includes the loss of something valuable. And you are being patronizing where you have no reasonable cause to be, given that you've apparently never been to law school. In light of the latter point, I have no further interest in this conversation.