Travel-Size Products 

The Rip-Off: Smaller is not better when it comes to travel portions of toiletries and the like. Example: a 3.2 ounce, TSA-compliant bottle of Listerine Total Care Anticavity Mouthwash retails for $1.99 at CVS, while a 16.8 ounce container costs $4.99. That means you are paying 62 cents an ounce for the travel-size bottle, more than twice the 30 cents an ounce for the larger one.

How to Avoid It: Pick up travel-size bottles (around 99 cents at The Container Store) and fill them up before leaving for the airport.

Wedding Gowns 

The Rip-Off: Alan Fields, author of Bridal Bargains, says that the convoluted ordering process for wedding dresses is kind to manufacturers and retailers, but not to consumers. "In any boutique a bride tries on a sample dress and is then ordered a dress to her approximate size," explains Fields. "The dress isn't being custom-made to her measurements, so it then has to be altered, adding on an average $200 to the already marked-up price."

How to Avoid It: Cut out the middleman and order direct from the manufacturer (there are a slew in China), then find someone to do the alterations.

Broadband Speeds 

The Rip-Off: Internet service providers are quick to sell you on the speed of their service, measured in megabits per second (Mbps). Comcast ( CMCSA - news - people ) offers a performance starter service with downloads up to 6 Mbps for $49.95 and a Blast service with downloads up to 20 Mbps for $55.95. You might think paying 67% less per Mbps is a great deal. But a report last summer from the Federal Communication Commission found that 80% of broadband users fall into usage categories that would require at most 4 Mbps, so chances are you'll end up paying for broadband you won't use.

How to Avoid It: If there's a trial period, test the service to see if it meets your needs.

Many Mutual Funds 

The Ripoff: Thousands of actively managed mutual funds(which employ stock pickers who try to beat the market rather than simply match its overall returns) charge fees of 1% or higher. Yet consider that less than 40% of actively managed funds that invest in large companies outperform the S&P 500 Index. Assuming an investment of $10,000 per year for 40 years, and an average annual return of 7%, a fund with a 1.5% annual fee compared to one with a 0.25% load will cost an extra $580,000. That's a yacht or a summer house.

How to Avoid It: There are plenty of mutual funds, index funds and exchange-traded funds that can be had for fees of 0.25% or less.

Extra Frequent Flier Miles 

The Rip-Off: Airlines routinely claim to be sold out of tickets that require fewer frequent flier miles, only to then sell you more miles to make up the difference. American Airlines (AMR - news - people ) charges $57.50 plus tax to buy 1,000 extra miles. Give a friend 10,001 to 15,000 miles and you'll fork over $150. Want to cancel a ticket bought with miles? That's another $150 to reinstate those miles. "Everyone in the industry knows that these programs are come-ons for consumers," says Charlie Leocha, director of the Consumer Travel Alliance. "But consumers have swallowed them hook, line and sinker."

How to Avoid It: Book ahead, travel in off periods and choose programs that include multiple airlines.