MY WIFE and I have season tickets for events at Carnegie Hall and Lincoln Center. At intermissions, we sometimes watch absently as three or four men in gray suits emerge from the wings to move a piano into place or bring out extra music stands and chairs.What they do is essential but unremarkable. Turns out that it is remarkably well-paid, however. Would you believe $422,599 a year? Plus $107,445 in benefits and deferred compensation?That is what a fellow named Dennis OConnell makes at Carnegie Hall. He is the props manager, the highest-paid stagehand.