I'm going to make an assumption so correct me if I'm wrong. You're looking at a Princess sailing that is sold out and have been offer the possibilty of being added to a waitlist. Princess seems to never actually close their sailings anymore, they just offer you a waitlist when they sell out. For most people a waitlist position is futile no matter the number. Waitlists open to allow them to sell cabins if there are cancellations. Most cancellation inside the penalty period happen within 48 hours of a cruise. That's when you realize you're too sick to go or their is a death in the family or some other tragedy that will prevent you from going. Remember, you can't just cancel and be refunded so there are very few cancellation inside penalty.
If they call you 24-48 hours before a sailing can you pack and get to the pier? If you need to fly, probably not. Also they won't confirm the price until you clear the waitlist. They can charge anything they want at that point. If you decline, they call the next person on the list. If you want to cruise, skip the waitlist and find another ship or sailing date. You'll be assured of having a cruise that way and be able to know the price and make other arrangements for transportation.