It's a time-honored way to lure shoppers into a store: Offer them something they can't get anywhere else. In the run-up to the holiday season, those "exclusive" deals are becoming more common -- but not necessarily more desirable.

Almost every store has limited editions and exclusive items on offer these days -- some of them whole product lines' worth. Toys R Us has so many proprietary items that, for the first time, the retailer sent out a 44-page fall catalog this month devoted entirely to its exclusives (including highly anticipated toys like Moshi Monsters and the Air Swimmer). Beauty retailer Sephora boasts in its recent marketing campaign that Dior's fall runway makeup and a special range of nail polish colors from OPI are only available at its stores. "It's a constant effort to get shoppers in stores, and exclusives are retailers' best way to distinguish themselves from their competitors," says Jim Bieri, an independent retail consultant.

The effort comes at a time when retailers are worried that consumers will stop spending, says Bieri. High unemployment combined with a jittery stock market has made consumers nervous, and exclusive products are a way to boost demand and business without necessarily dropping prices. To that end, many stores are focusing less on offering one product but on an entire line or range of goodies to generate more buzz, says Jim Silver, editor in chief of TimetoPlayMag.com. Consider Target, which in September launched a collection with Italian fashion design house Missoni. The company's stores sold out of the items, which included throws, tote bags and dresses, within minutes of opening and crashed Target.com for a full day.

But what's good for stores may not be good for consumers. Exclusive deals means stores don't have to meet a competitor's deep discounts, or offer any discount at all to make the item attractive, says Silver. And even if the item goes "on sale," it's not easy to tell how good a bargain you're really getting. The store might have planned the original price of say, $50, knowing that it would offer a $5-off coupon right away, says Silver. Shoppers are also more likely to over-spend on an exclusive item, says Michelle Madhok, founder of sale site SheFinds.com. Some get swept up and purchase more than they intended; others visit for one item they can't get anywhere else end up buying other stuff, too.

To avoid paying too much, experts say shoppers should adjust their habits, especially as the holidays approach. Although discounts aren't common, some exclusive items do go on sale -- the Toys R Us catalog included more than a dozen coupons. Madhok says shoppers might also check rebate portals like Ebates, which is currently offering 8% cash back at Sephora, or buying secondhand gift cards from resellers like CardAvenue, where cards for Best Buy sell at 5% discounts. Also, check around: Often exclusive items differ only in minor details (like color) from ones sold cheaper elsewhere.