It's a quiet day here on Majorca so I just had a look at the maiden out of curiosity. There are huge numbers of all grade cabins available, far more than on my December 2023 Arvia cruise.
Could perhaps the date be a problem, ie mid December arriving back 23 December? Often not a popular time to travel with the holidays coming up with all that entails and the prices are as Binman says verging on extortion!