We just upgraded on the May 23 Wonder from a cat. 5 to a cat. 3. They said it was very unusual for a cat. 3 to become available, someone had cancelled at the last minute. After you are checked in you go to the desk at the end of the check in row, by the line at the big yellow mouse ears. If there are any upgrades available they go by a standard upgrade chart in order to determine the price of the upgrade. We were already in a cat. 5, so to go from a 5 to a 4 was $298.00, then a 4 to 3 was an additional $598.00, a total of $896.00. WORTH EVERY PENNY! Huge room, concierge service, two full bathrooms, etc... (not like what is referred to as two bathrooms in a cat. 5, these were two large bathrooms on opposite ends of the suite.) So the price is determined by how many categories you have to move up. It did take them until about 5:00pm to locate all our luggage at our old room and get it to our new room, but so what!
Also, we more than doubled the recommended tip for the stateroom host because the room was more than double the size of a regular room and had two full bathrooms to keep clean. Rudy did a fabulous job!