Show tickets are nice, run about $150 for a pair of descent seats.
The most important thing is to make sure that your clients were 100% satisfied so that they will refer you to a friend. I'm pretty sure that a greater majority of people find their agents through a friend referral.
Oh - you meant, for US to buy THEM.
True story. Colleague shaved half a point off the listing fee to put the deal together; they bought out of state, came back to a party with mutual friends. They caught up with Colleague, told them how wonderful their new home was, and how great their new agent was. "Do you know what my agent did down there? She made up a bunch of mailing labels with our new address on them!" Colleague asked them, "Do you remember what I gave you as a closing gift?"
I think too extravagant a gift sends the wrong message. In any market.