From the itinerary, the cruise looks to be about 13 days minimum to make the listed port calls. Calculating the bottom line on airfare, I'd class it as a bargain brought on by modestly hard times in the cruising industry (the economy aggravated by the CONCORDIA grounding).

Depending on the "Up Sell" cost of a balcony, for me at least a sort of necessary evil on that long a cruise, it seems a good deal, especially if you can figure out how (with no extra air cost) to get to SJU a day or two early, and stay for a few days in BCN, in my eyes the SFO of the Med.

San Juan/Canarias/Gib is a routing which avoids the more turbulent belt of the N. Atlantic. I wouldn't worry much about the sea state, and the scheduled port calls are attractive.