NEW YORK -- That cheeseburger on the value menu may end up costing more than you think.

Whether it's the "Dollar Menu" at McDonald's or the "Why Pay More Menu" at Taco Bell, fast-food chains often spotlight their cheapest offerings to attract customers.

The items usually cost a buck or so and are no doubt a deal if you're looking for a quick treat. But there's a reason why companies dangle the offers; customers often end up spending more on other items once they're in the restaurants. Think $3 coffee frappes and fruit smoothies.

"Every restaurant has an opportunity to get customers to trade up to more expensive, higher-priced options including main entrees, sides, beverages and desserts," said Darren Tristano, an analyst at research firm Technomic.

Additionally, value menus aren't as filling as they were a few years ago because restaurants swap out items that become too expensive to offer at such low prices. Earlier this year, for instance, small fries and small soft drinks disappeared off McDonald's Dollar Menu.

That doesn't mean that you should stay away from value menus. After all, you get deals on certain items because restaurants make money on others.

But as a consumer, it's worth knowing how fast-food chains rely on value offerings – and the role they play in how much you ultimately spend.

FILLING UP THE TRAY

For restaurants, the profit margins for value menu items are often razor-thin. But they make money off them by selling the items in huge volumes.

Taco Bell, for example, is known for its affordable prices even in the fast-food industry; its "Why Pay More" menu offers 89-cent nachos and 99-cent tacos.

But chances are that you'll get more than one taco. Not including a drink, customers order an average of three items, says Brian Niccol, the chain's chief marketing officer.

Better yet, customers may opt for (relatively) pricier items, such as a grilled stuffed burrito, which is around $3. Or they might "trade up" to the new taco that comes in a Doritos flavored shell, which costs 30 cents more than a regular taco. The idea is that people will fill up their trays, hopefully with more profitable foods.

The same philosophy applies to other fast-food chains, including Subway. The ubiquitous sandwich shop doesn't have a value menu per se, but its $5 foot-long deal has become a staple of its marketing. Without giving details, Subway Chief Marketing Officer Tony Pace said the offer has been a "game changer" in terms of bringing in customers since it was introduced in 2008.

And as customers wait for their sandwiches, they may be tempted by the variety of chips (about $1 a bag) that line the counter or the cookies (three for $1.39) by the register.

WOULD YOU LIKE A DRINK WITH THAT?

Whether you choose to order a drink with your meal makes a big difference to fast-food chains. That's because fountain drinks have high profit margins.

"The more often you can sell a drink, the better you feel about providing discounts on other items," said Niccol of Taco Bell.

In the past year, however, customers have kept spending in check by ordering only food or requesting only tap water, according to a study by The NPD Group. As sales of sodas and diet sodas have slipped, restaurants have responded by aggressively marketing other drinks, such as specialty coffees and smoothies.

It's been a big part of McDonald's success in recent years; the chain introduced premium coffee drinks in 2009 and fruit smoothies the following year. It's no surprise that Burger King followed suit with its own coffee frappes and smoothies as part of its revamp earlier this year. Wendy's is also testing specialty coffees in select markets.

At Taco Bell, customers can get a Fruitista Freeze, a frozen drink topped with fruit pieces, or Limeade Sparklers, which is lemon-lime soda and lime juice.

"There's definitely a consumer trend of splurging on drinks," says Niccol of Taco Bell.

In fact, "beverage only" trips to fast-food restaurants are increasing, according to The NPD Group. These trips are often for shakes, smoothies, slushy drinks and coffee.

SKIMPIER MENUS

Value menus aren't as meaty as they once were, either.

When McDonald's first introduced its Dollar Menu a decade ago, for example, the flagship offering was the Big `N Tasty, made with a quarter-pound beef patty. But as McDonald's and other fast-food chains pay more for beef, cheese and other ingredients, what customers can buy for just a buck isn't quite as filling.

The Big `N Tasty lasted on the Dollar Menu for about a year. McDonald's then added the Double Cheeseburger, which has smaller patties, to the lineup instead.

About three years ago, McDonald's took the Double Cheeseburger off the Dollar Menu and replaced it with the McDouble, which has one slice of cheese, instead of two.

As ingredient prices have risen, McDonald's in March introduced its "Extra Value Menu," where items cost closer to $2. That's where the two-cheese-slice Double Cheeseburger is now found.

"What it boiled down to was our ability to offer our customers options that make sense for them, but also make sense for us," says Danya Proud, a spokeswoman for McDonald's.

The changes may be why the Dollar Menu now makes up about 10 percent of McDonald's business, down from about 13 percent in earlier years.

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  • 10: Chick-fil-A, $4,051,000,000

    Although Chick-fil-A has recently found itself <a href="http://www.huffingtonpost.com/2012/07/30/chick-fil-a-brand-approval-rating-anti-gay-controversy_n_1719359.html" target="_hplink">embroiled in social controversy</a>, it managed to make the top ten in 2011.

  • 9: KFC, $4,500,000,000

    Although KFC lost 275 locations last year, they still managed to remain in the top ten in 2011.

  • 8: Pizza Hut, $5,500,000,000

    Pizza Hut came out on top in a <a href="http://www.huffingtonpost.com/2011/07/27/pizza-hut-ads_n_911106.html#s316917&title=Super_Sincere" target="_hplink">study on ad effectiveness in 2011</a>. An ad for the chain's Ultimate Stuffed Crust Pizza made consumers the hungriest.

  • 7: Dunkin' Donuts, $6,500,000,000

    With 115 new locations, Dunkin' Donuts had the second largest location growth in 2011 (beaten by Subway by an insane margin -- they opened 872 new locations).

  • 6: Taco Bell, $7,000,000,000

    Taco Bell's 2011 started out turbulently, with a well-publicized lawsuit surrounding the content of their beef. They counteracted the suit with (among other measures) <a href="http://www.huffingtonpost.com/2011/01/28/taco-bell-beef-meat-lawsuit-ads_n_815303.html" target="_hplink">full page ads in the <em>New York Times</em> defending their meat</a>, managing to right the ship and have a great year -- even before the launch of this year's famous <a href="http://www.huffingtonpost.com/2012/06/05/doritos-locos-most-popular_n_1571160.html" target="_hplink">Doritos Loco Taco</a>.

  • 5: Burger King, $8,400,000,000

    Burger King hopped on the avocado band wagon last year, which was only one of many changes the chain underwent, including the <a href="http://www.huffingtonpost.com/2011/08/19/burger-king-de-thrones-king_n_931208.html" target="_hplink">dethroning of their mascot, The King</a>.

  • 4: Wendy's, $8,500,000,000

    It seemed likely that <a href="http://www.huffingtonpost.com/2012/03/19/wendys-burger-king-number-two_n_1364514.html" target="_hplink">Wendy's would dethrone Burger King to become the second biggest burger chain in the U.S.</a> -- and it turns out, they totally did.

  • 3: Starbucks, $9,750,000,000

    Starbucks closed the most locations of any of the chains in the top ten last year, shuttering 310 locations. In 2011 the chain also <a href="http://www.huffingtonpost.com/2011/01/17/starbucks-new-size-trenta-graphic_n_810083.html" target="_hplink">rolled out its insane, 31oz Trenta size</a>.

  • 2: Subway, $11,400,000,000

    Subway was recently crowned both <a href="http://www.huffingtonpost.com/2012/05/10/best-fast-food-restaurants_n_1507319.html" target="_hplink">America's favorite fast food restaurant</a> and its <a href="http://www.huffingtonpost.com/2011/03/07/worlds-largest-restaurant-chain-subway_n_832511.html" target="_hplink">biggest chain</a>. Opening 872 new locations in 2011, their total number of U.S. locations rose to 24,722, nearly beating McDonald's and Starbucks combined.

  • 1: McDonald's, $34,172,000,000

    Well, no surprise here, right? While no longer the largest fast food chain in America, McDonald's is surely the most successful -- their 2011 U.S. revenue beats Subway and Starbucks' totals combined. A recent American Consumer Satisfaction Index survey revealed that the chain is, however, <a href="http://www.huffingtonpost.com/2012/06/21/mcdonalds-low-customer-satisfaction_n_1615606.html" target="_hplink">at the bottom in terms of customer satisfaction</a>, so McDonald's may not reign forever.