When Brian Greenberg booked a Spirit Airlines flight from Phoenix to San Juan last year, he thought he was getting a great deal.

Greenberg, who owns an insurance agency in Scottsdale, Ariz., was going to fly to Puerto Rico to take a Christmas cruise to the Caribbean. But high-season airfares were running more than $1,000 per person round trip. Spirit, which bills itself as an ultra-low-cost carrier, had tickets for about $200 less than the going rate.

“The trip had two stops, but the price was too low to pass up,” Greenberg says. He even paid extra for an upgrade to Spirit’s premium cabin.

But at the airport, Spirit charged Greenberg extra for his checked bags because they weighed more than the stipulated 40 pounds. And that wasn’t his only surprise.

“The seats didn’t recline and were smaller than any other flight I’d ever traveled on,” he recalls. “There was a fee for everything on the plane, including water.”

Greenberg expected to spend about $936 per person on the flights. But with all the extra charges, the per-ticket cost had increased by 33 percent to $1,249. The $939 in combined extras for Greenberg and his travel companions included $462 for checked bags, $150 for overweight baggage, $318 for the seat upgrade and $9 to join a fare club to qualify for discounts on bags and seats. He says a major airline would have been cheaper, not to mention more comfortable.

“It was not a deal,” he says.

Greenberg’s reaction is common. “I hear the horror stories all the time,” says Mitch Krayton, owner of Krayton Travel, a Denver-based agency. “The temptation for a deal is great. But you must do your own research, and you own the consequences of your choice.”

Deals can be a matter of perspective, of course. Another Spirit passenger might have traveled without checked luggage, stayed within the weight limitations and skipped the cabin upgrade. For that person, the flight would have been a great deal.

How can you avoid making such a mistake? Experts prescribe careful research, including a review of the fine print, and a reality check. (Is it too good to be true?)

Take Greenberg’s flight, for example. Spirit Airlines has a well-deserved reputation for offering a low initial price and then adding fees. It’s a way to make you think you’re getting a bargain when you may not be. But Spirit discloses the creative surcharges on its website. Those include overweight baggage fees that kick in at 40 pounds instead of the industry standard 50 pounds.

Some travelers tend to do a lot of research on the front end. They spend hours online looking for the lowest price. But when they find it, they assume the hard work is over. They’re wrong; it’s often just beginning.

“If you find a travel deal that interests you, be sure to do your homework before you agree to book,” says Angela Rice, co-founder of Boutique Travel Advisors, a travel agency in Paradise Valley, Ariz. “Research the reputation of the company, verify the location of a hotel, check out reviews and visit websites directly.”

Even if something checks out, keep digging. Laurie May wishes she had. She disembarked after a recent Oceania cruise and discovered an unexpected $320 charge on her folio. The charge, which turned out to be automatic tips for the crew, made her vacation a little less of a bargain.

May, who works for a nonprofit organization in Potomac, Md., says she never had an opportunity to decline the automatic gratuity. “They say in their brochure that gratuities are discretionary and that passengers can have the gratuities removed or changed while the passenger is on board,” she says.

In fact, the cruise line’s terms and conditions say it automatically adds a gratuity of $16 per guest per day. It also adds an 18 percent “service gratuity” for all beverage purchases, spa services and dinners at its premium restaurants. “Naturally,” it adds, “guests may adjust gratuities while onboard the vessel at their sole discretion.”

May had already disembarked. In an email to her, the cruise line said she should have reviewed her folio before she left the ship. It couldn’t refund the tips, the email said, because “we have already disbursed the gratuities among the crew.”

You’ll find a lot of surprises hiding in the fine print. They range from mandatory hotel resort fees to “tire disposal” fees charged by car rental companies. You can find them by reviewing the information on your screen carefully before you click the “book” button.

Even so, wishful thinking is a powerful thing. Consider what happened to Torben Lonne, who found an incredible bargain at an all-inclusive dive resort on Mafia Island in Tanzania. The $150-a-night price included all diving and meals.

“The name of the island should have made the alarm bells ring,” says Lonne, who edits the online dive magazine Dive.in. “But we were convinced it was a great place.”

Spoiler alert: It wasn’t.

It’s easy to see why consumers are eager to save money on travel. The problems start when that eagerness makes them forget the “too good to be true” rule: If something looks too good to be true, it probably is.

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