I have to agree with Robocop. If you booked with Carnival, I understand that they do offer a lowest price guarantee if they drop their own prices. Of course, you'll find that TAs can usually beat the Carnival prices.
Unless you have a "lowest price guarantee," when you buy your cruise you're purchasing a ticket at that specified price. As you get closer to your cruise time, you'll probably see even more special prices on empty cabins. . . it can be very frustrating if you were hoping for the very best deal -- but only Carnival knows what the very best deal will ever be (and on which cabin??) on any cruise.
That's one of the reasons that comparing ticket prices on cruises is sometimes considered to be in poor taste. You don't want to spoil your own or someone else's cruise by finding out that they got a much better deal on the same cabin. If everyone compared tickets, they'd vary widely (just like airplane fares on the same plane).
On the good side, most Carnival cabins (except the suites, and inside versus outside) are essentially the same. Only the deck changes. Since some people prefer the lower decks anyway since they're supposedly more stable and/or closer to the embarkation decks for port visits, and some people prefer the higher decks since they might be closer to certain amentities, there's something for everyone without anyone feeling that they're short-changed.
Since you booked a category 8, I'd enjoy my category 9 and stop looking at the prices. Just pack and enjoy the trip.