Jonas Kaufmann will no longer sing at London’s Royal Opera House — because, of all things, the pay is too low. “ I don’t know how you do it ,” the tenor recently told BBC Radio 3. In the same interview, he revealed that he won’t bother singing at the Metropolitan Opera anymore, either, though that’s about ideological differences. For a singer like Kaufmann — arguably the biggest star in all of opera — to swear off two of the world’s top-five opera houses is not merely eyebrow raising. It is