You can get tickets for the opera in Zurich at far cheaper prices by getting up early and queuing for the periodic "Volksvorstellungen." Tickets go on sale one month before a particular performance, so it's a matter of checking the schedule for which evenings are Volksvorstellung, then figuring out the date tickets go on sale and getting there early to get the best tickets. We usually get category 4 - quite high up but acoustically brilliant - for around 25.- a ticket.

By the way, early really means early, even by Swiss standards. There is a loosely organized group of retirees - a cultivated but merciless gray panther mafia, really - who get there especially early and wait outside until the box office opens to make sure they get the best seats.