We just came off the Sydney to Auckland run of the Millenium where we ate in the Olympic Diningroom. The upcharge was $30.00 pp and in my opinion it was a steal! Outstanding service and menu. On your chit that you sign there is a space for an additional tip should you wish. I think we tipped an additional $30.
That meal which lasted over 3 hours would easily have cost me $200 on land so $30 is a no-brainer.