The price goes up according to the deck...the higher, the more expensive even though it is exactly the same size cabin. There are no single cabins so of course 2 cabins is more expensive than one cabin.
Depending upon your budget you may want to look into the larger suites. In our case we always opt for the least expensive midship cabin and are perfectly satisfied. (we would prefer to be on a lower deck even if the prices were the same).
I'd love to hear more about you. What cruises have you been on thus far? What is the longest cruise you've taken? Are you a Doctor (we have several on this board) or is this just your screen name?