You may want to post in the "bargain finder" to compare prices, its hard to tell if thats a good price or not?? Did you do any shopping around before you found this cruise? I find if you are happy with your travel agent and get good service, thats a big plus, enjoy the "Grand".
Sounds like you are paying too much. I sailed the Grand in high season of March at $1187 pp including port charges & taxes for a Cat. CC guarantee and received a balcony cabin on Aloha deck. Now the 3rd passenger no matter what age will pay less. Keep in mind triples are limited and you may need to pay more for that premium. Then add you air which is easily checked on travelocity.com or expedia times 3. If you find a triple cabin available in you comparison (just treat it as a brand new booking), go back to your present TA and let them know exactly what you have from another agent. If they will not match it, bring your business elsewhere.
The prices will probably go down about 2 months before your cruise and you should be able to get a refund for the difference. Call your TA and ask them if this is their policy.If it is keep your eyes out for when the prices drop. If its not you may want to consider getting your money back and going with an agent who will refund price drops.
It seems pretty high but then again, I don't know where you are flying from and what class and I don't know your cabin Cat either, all of which can make a considerable differance in the cost. What I suggest you do is to check with some TA's and see what they have to offer for the same thing and see if it is comparable in pricing. You may also wish to list your cruise, (be specific), in the Bargain-finder area and see what the responding TA's have to offer. Pick a TA that you feel comfortable with that you believe will provide you good service and a good price.