I wholeheartedly agree with all the great information and advice you've already been given.
Between the problem with the Costa Concordia and the problems in Athens and Cairo, it scared alot of people away and that drove prices down. Unless something dramatic happens, I can almost guarantee you will not see prices anywhere near that rate this year.
It's best to book the ship, date, and itinerary you want with your agent and then keep your eyes open for any specials that may occur. For example, Celebrity is offering some great rates and amenities right now through January 27th. But if the rates don't come down, then you can make a decision before the final payment due date if you want to go or not. You definitely do not want to be making airline reservations less than 60 days prior to sailing - the rates would be sky high, so to speak.