When we went, we simply booked a room for the night to get the guest passes. No, it wasn't cheap, but we got to use all of the facilities and they really are outstanding.
The least expensive room that we could book came to about $180. There were 3 of us so that came to about $60/person. That's not too bad for a full day of entertainment as well as the best facilities you could imagine for keeping our clothes and changing for dinner. I'm sure that the other passengers thought we were heading home when we left the ship with our luggage for a one day excursion <G>!