I know I'm late, but here's an opinion from someone who lives in a black and white world
The person who asked if anyone would like to go owes the first thank you. The person with the ticket asked the favor. It shouldn't matter that it's a "good" favor because it's a concert. If you asked someone to move a couch, you owe the person that helped a thank you. Just because it's pleasant doesn't make it any less a request.
Now, if the other person said "Ohhh, I hear you have tickets to this concert and I want to go. Please, can I have the other ticket?" - then the other person owes the ticket holder the thank you because they made the request of a favor.
See - black, white, black, white. Simple!