I signed up for a spring break cruise out of San Diego on Koningsdam when they rolled the standby program out last year. Much to my surprise two days before they confirmed my booking, they offered me a paid upgrade which I declined, and I packed my bags. Had a great time in my sideways inside cabin. Including standby fare, excursions, gratuities, and on board spending I spent a week on vacation for under $1000. There is not a solo supplement for the standby cruises.