It's not unusual to see a cruise line raise the rates before offering a 'big' sale. They all do it and it's done all the time.
Had a client who booked a cruise last week and the next day there was a special in which they could get $50 onboard credit per stateroom. So I checked out the rates and found they had gone up $100 per stateroom. Naturally, I gave the client a choice; you can keep the rate you have and forgo the onboard credit, or I can get you the $50 onboard, but your rate will go up $100. Gee, now there's a no brainer!
But I see this all the time because, as your mother always told you, you don't get something for nothing.