> You can only do that if the transaction is atomic, which requires that the tickets and money are on the same blockchain and exchanged in the same transaction

> You can only do that if the transaction is atomic, which requires that the tickets and money are on the same blockchain and exchanged in the same transaction. Yes, they should be on the same chain, so that the transaction is atomic. This is trivial to do in Ethereum (and other blockchains, presumably).