When you're booking a cruise, be sure you understand what is not included in the price. The ad may list it as less than $100 a day per person, and go on to insist that a similar top-rated hotel or resort vacation would cost considerably more. Most cruises are advertised as all-inclusive, and the boast that they are bargains is true ... up to a point.

Unlike all-inclusive cruises, the typical land-based vacation requires food, entertainment and other features to be purchased separately. Most cruises really are bargains, but those all-inclusive packages are not all you'll pay. Some features that may cost extra include: 1. Liquor and soft drinks: Not usually free, whether at meals, by the pool, in piano bars and elsewhere on the ship. On most cruises, passengers who order mixed drinks pay between $7 and $10 each. Sodas are $5 each, although there's a never-ending soda cup that could be purchased for $10 and used throughout the cruise. At meals, buffets and other areas of the ship, there are no charges for all-you-want citrus ades, juices, coffee and tea.

2. Special dining rooms: All meals and most snacks are included in the original price, but many cruise ships also offer special dining rooms for those who want more elegant menus and atmosphere. The extra charge for those exclusive meals is from $25 to $50 each.

3. Spa facilities: While the pool and whirlpools on deck are free, there are charges for massages and other types of individual spa treatments. The costs range from $25 to $100 per session.

4. Excursions: One of the most attractive features of a cruise is the array of shore trips available when the ship visits ports. They could include historic tours to ancient ruins, snorkeling among dolphins and souvenir shopping. The excursion costs range from $50 to $200 each.

5. Tips: Gratuity expectations vary from ship to ship, but are always expected by an array of cabin stewards, bartenders, spa employees, waiters, head waiters and excursion guides. These tips, ranging from $5 per cruise day per person, are traditionally handed out on the last evening. Some ships simplify the process by allowing passengers to pre-pay tips all into one amount to be charged to their on-board account.

6. Various add-on charges: The original price quote for your cruise quickly rises because of various taxes, port charges, cell phone roaming costs, rental of onboard computers and other items that are not specified in ads. They could add another 10 to 25 percent to the original advertised price.

Some cruises, such as last-minute specials and package deals (flight and cruise combinations), may not charge for some of those items as inducement to late-sign-on passengers and avoid sailing with empty cabins.

Despite the added charges, cruises may still be bargains. You’ll undoubtedly agree during your next cruise, when you’re at the dinner buffet on your fourth helping of all-included broiled lobster tail, topped off with three pieces of cherry pie a la mode.