Check the Math on Air Fares

"Fly to London for $198!" The advertisement seemed too good to be true.

And it was -- once you factor in all the hidden taxes and fees.

For the last month, British Airways held a big off-season sale on travel to and from Europe, offering flights to London for as low as $198 roundtrip. The deal was so good, travelers were doing double takes looking for the catch. And of course, as with most sale fares, there were a number of catches -- taking advantage of the $198 roundtrip wasn't easy.

In order to receive the absolute lowest fares, travelers had to depart and arrive on Mondays, Tuesdays or Wednesdays. Roundtrips with arrivals and departures on Thursdays and Fridays cost between $258 and $298. Some roundtrips on Saturdays and Sundays -- two of the more popular arrival and departure days -- cost as much as $1,400.

And even if you were able to fly early in the week, those rock-bottom roundtrips rapidly sold out, especially in October and November, putting the starting price of the cheapest roundtrip at $258, instead of the advertised $198. And these are just the advertised list prices of fares -- none include the blizzard of taxes and fees shoveled into the price you actually pay, which significantly jack up the price of an international ticket.

When all was said and done, that $198 roundtrip actually cost more than $300.

"It's like your phone bill, how the phone is $12 a month, but it ends up costing three times that after they add in all the little fees," said Brian Barth, CEO of SideStep, an online travel search engine.

A Taxing Equation

Even professional travel agents have trouble figuring out taxes and fees, with airports and governments all demanding a tiny sliver of the travel pie. Also, carriers charge all kinds of different rates and fees for fuel, security and even little extras like $20 for paper tickets or $100 for an oversized bag.