The question "how much is it to book a cruise?" refers to the financial cost associated with reserving a spot on a multi-day sea voyage. It is a type of noun phrase that functions as a subject in a sentence, as in the example "How much is it to book a cruise to the Caribbean?"
Determining the cost of a cruise is crucial for budgeting and planning a vacation. It can vary widely depending on factors such as the cruise line, itinerary, cabin type, and time of year. Researching and comparing prices from different providers can help travelers find the best deal for their specific needs.