You are confusing possession with ownership. The buyer owns the tickets from the moment the purchase is complete, whether or not he has received them. If the

You are confusing possession with ownership. The buyer owns the tickets from the moment the purchase is complete, whether or not he has received them. If the tickets went down in value in the interim time, then the most expedient thing for the seller to do to cure the problem would be to buy new tickets at the now-reduced price and hand them over to the buyer. You are absolutely right, the buyer can't demand his money back if the tickets go down in value -- he has to accept tickets that are fundamentally the same in value as the ones he was supposed to get. Now, if for whatever reason the seller couldn't replace the tickets even though the price has dropped (unlikely -- that's pretty much the definition of a price, is that the item is available in exchange for money), then he might be able to ask for his money back instead.