To the OP, yes, he scammed her. Even though the woman set value to the item, the tickets' actual value is only what the seller paid for them. eBay's Terms of Service do not set a binding legal contract between buyer and seller, so she was not under any legal obligation. Yes, she was a rude buyer who backed out. To get her to pay he could have attempted to sue in small claims court. Maybe the threat of that would have gotten results. It sucks that there wasn't time to resell and the seller was nasty about it, but the two negatives of being unethical to get justice on someone who was unethical don't cancel out. Both were in the wrong.
That being said, I love a good scheme