You may want to look at cruisefish.net - Click on Finder and then select the ship and sailing date. If the rates listed are in black, the rates are still opening day rates. If red, they've gone up since. You can hover over the rate and it will display the changes.
Do not pay attention to the EUR or GBP rates as those will change depending on the exchange rate.
Rates that show greyed out are categories sold out.
Prices shows are per person for the first or 2nd passenger.
Kids will be less.
Even if a cat shows available, it might not be when booking due to muster stations capacity.
For example, 3n Dream for July 3rd, are still showing opening day rates for verandah staterooms. Inside/oceanview are higher. But you are looking at $1180 per person for the first two adults.
October 2nd rates are already higher than opening day rates, but they are more than half the price of the July rates. Opening day rates for verandah started at about $525 p/p instead of the current rates of $555
Hope this helps...