Return the names of artists and the themes of their exhibitions that had a ticket price higher than average.
SELECT T1.theme ,  T2.name FROM exhibition AS T1 JOIN artist AS T2 ON T1.artist_id  =  T2.artist_id WHERE T1.ticket_price  >  (SELECT avg(ticket_price) FROM exhibition)
Sanatçıların isimlerini ve ortalamadan daha yüksek bir bilet fiyatı olan sergilerinin temalarını iade edin.