When shopping online, you may have noticed that sometimes one critical piece of information is missing from the otherwise detailed product descriptions—the price. You have to put the item in your cart for the big reveal. Why the suspense?

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This practice is not necessarily a tactic to trick you, but rather an indication that the retailer is charging less than the minimum price some manufacturers impose on their merchandise, says Eric Goldman, a professor at California’s Santa Clara University School of Law and a specialist in internet law.

Retailers that advertise prices below the minimums risk manufacturers’ ire—and the possibility that the manufacturer might cut off their supply. But a retailer that doesn’t actually advertise the price—for example, by making you go fetch it—may not be violating the manufacturer’s minimum price policy, or may be hoping the manufacturer either won’t notice or will look the other way.

Editor's Note: This article also appeared in the December 2017 issue of Consumer Reports magazine.