We'll be sailing with you on May 7. Sound like you got a good deal. Our total was 2,500 for 2 adults and 2 kids. I guess the kids are a little cheaper than adults. We too were wondering if we got a good deal.
I checked my favorite search engine at www.vacationstogo.com, and $749 plus port charges and tax was the price they showed. They've generally managed to undercut just about everybody except my travel club.
I think the inside price they show is the lowest inside category, which is generally down in the bowels of the ship. If you can get an upper deck inside at this price, you did good. If you're in the lower decks, they're not that bad and generally have less rocking motion than the upper decks. However, there may be more noise...take a look at the deck plans for that ship and see what's above and below you.
Sailing single, I book inside cabins alot and if you have to do inside, Princess is the cruise line! The cabins inside on the lowest deck are not really so far from the rest of activity or civilization like other cruise lines!
Usually the last ones are on Plaza which also has access to an atrium level and possibly a dining area so you aren't removed away from it all. On Celebrity Millie class ships, I had an outside cabin and I still felt like I was in the ends of earth, it was not a good thing!