Due to world economic factors, and the price of fuel, many cruise lines have been forced to implement a fuel surcharge to cover the additional operational expenses.
Most recently, Lindblad Expeditions recently announced that due to a decision made by the President of Ecuador ending subsidization of the cost of fuel in the Galapagos, they are forced to implement a $150 per person fuel surcharge on all Galapagos reservations effective for cruises embarking on or after June 1, 2008. That is a fairly sizable increase to the amount of a cruise.
Be aware that as the price remains at the current level or rises further, other cruise operators will likely follow suite.