Tips. The one "extra" you really can't avoid is tipping. CruiseCritic estimates this expense at about $12 a day, per person, with hardly any line-to-line variation. Some lines are now adding about that amount to your bill automatically unless you tell the line you want to change the figure.
Latte. Again, basic nonalcoholic drinks are normally included, but you pay extra for a specialty item such as a latte. The cost ranges from $2.50 to $5, averaging about $3. A latte is easy enough to avoid but $3 isn't a bad price if you like one.
Massage. A 50- to 120-minute massage runs anywhere from $120 to $200. It's easily avoided, but the prices aren't over the top if you want one.
Shore Excursion. The price of a shore excursion in St. Thomas, a typical and popular island port, ranges from $55 to $70, with most coming in around $60. If you want an organized shore excursion, that's not a bad price. You can usually beat it a bit by buying excursions, in advance, from a specialist tour agency such as viator.com, but you won't gain much. The best way to beat shore excursion prices is to buy from an operator at the pier when you arrive, or to organize your own taxi trip. Even better, in some ports, you can use public transportation or just walk.
Fitness class. If you really feel like it, you'll pay $12 on most lines. No big deal.
Souvenir Photo. Prices for an 8-by-10 photo range from $9 to $30, with most coming in near $20. This is a pure rip-off: The photographer hounds you throughout the cruise, for a result that you probably stick in a drawer once you get home and never look at again. If you need a picture, have someone take it with your own camera or phone.
Bingo. Prices and plans vary a lot, but figure anywhere from $6 for one card to $30 for more play. Overall, the experts tell us that shipboard casinos are a lot less generous than those in Vegas.
Internet. Keeping online on a cruise is expensive. Typical plans call for a minimum of $55 for 90 to 100 minutes, with the cost averaging out to $34 an hour. That's a lot more than you pay for WiFi on airlines these days, but, as Sam Scheele noted, "being online is like the hard stuff," and if you need an Internet fix, you can get it -- for a stiff price.
In Sum: Cruising can be one of the best-value vacations anywhere. But, as with any sort of vacation, you'll never run out of opportunities to overspend. The basic rule: Have fun, give yourself a daily limit for extras, and keep to that limit.
(Send e-mail to Ed Perkins at eperkins(at)mind.net. Perkins' new book for small business and independent professionals, "Business Travel When It's Your Money," is now available through http://www.mybusinesstravel.com or http://www.amazon.com)