You can get some excellent rates on 4 night cruises if you watch for them to go down. We did 4 nights Key West/Cozumel, and 4 nights Nassau/Freeport and got really good rates. This 7 night one we're going on is a steal for the price we got. (342.80 per person, FL resident rate) I've posted before that I use expedia.com or vacationstogo.com, and when I find a good rate I call the cruise line directly to see if they can do better. They always have
There was an awesome deal for past guests---$186 per person including taxes/fees---on Sensation 1-28 that I passed up to go on Victory the same day. You just have to watch for the best deals. Good luck!!
Sovereign of the Seas, Royal Caribbean 11-17-03
Fascination, CCL 2-14-05
Fantasy, CCL 2-05-06
Elation, CCL 9-24-06
Carnival Victory, CCL 1-28-07
Sovereign of the Seas, Royal Caribbean, 9-24-07