I think it would depend upon how many are in your party.
We just upgraded from a cat. 4 to cat. 3 for our May 10th cruise, it was about $2500. more that is for 5 of us, 2 adults and 3 children.
We were on the waiting list, but I was told by a CM to call instead of waiting for the waiting list, especially around the time final payments are due. On one of my calls a CM told me that a cat. 3 was on hold, and if the deposit wasn't received it would be released. We called the day after the deposit should have been received, and the cat. 3 was available !! woohoo !
Have a Great Trip !