There are probably as many ticket package options for cruises as there are usage plans for cellular phones. One option would be the "glutton package" where you pay a fat price up front but get unlimited amounts of whatever you wish to partake of at no extra charge. On the oposite end is the "mizer package" where you pay for a berth and everything else is extra. If a cruise is poorly booked, the cruise line is probably happy to give away a berth that would otherwise be empty in hopes that they'll make money from whatever other goods or services you purchase while on board. If you don't mind making your own bed and eating home-made bologna sandwiches, you could probably have some fun at very little expense. But I would expect some subtle pressure from the crew aimed at getting you to spend money.