I would have assumed it was free as well if no payment was asked for up front. Definitely not right of him try and unload a ticket like that.
If its a good friend of yours though, I don't think its worth ending the friendship over, which seems to be part of the question as well. It may just be a simple misunderstanding, at least let him explain in himself. For your part, I'd let him know that his actions were not cool, and in the future if he pulls another bait-and-switch like that, its going to compromise the friendship.
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