Shopping online isn't like visiting a store — different users could see different offers based on a variety of factors.
Shopping online isn't like visiting a store — different users could see different offers based on a variety of factors. - 

Here's some not-so-happy news as the holiday shopping season continues: The price you see online for a given item may not be the same as the price others see. The retailer may ask you for more money, or just show you an array of more-expensive products, depending on what kind of machine you’re using, or whether you're logged into their website, or your browser. That’s the bad news from a recent paper by researchers at Northeastern University.

The worse news is: It’s really, really hard to tell what conditions might get you the best price. 

Earlier reports had documented individual quirks: Staples might charge you a $1.50 more for a stapler depending on your ZIP code. The CEO of Orbitz once acknowledged steering Mac users to fancier hotels.

This study was more rigorous, and it found systematic differences in which users see what products, at what prices. The systems were tricky to detect and would be super-hard for consumers to game. 

"Initially, we assumed the best thing was just going to be ‘clear your cookies,’" says Christo Wilson, a computer science professor and one of the study's co-authors. "But it turns out to be much more nuanced than that."

For instance, clearing your cookies gets you slightly more-random results on Expedia. Android customers see higher-priced items when they search Home Depot, and sometimes the same items at a higher price. Travelocity seems to offer better deals to iPhone users.

That last part — different prices for different customers — is called price discrimination. Which sounds bad, but in general is actually really popular.

"This happens all the time in the real world," says Wilson.  "People get discounts, there’s coupons — people love it.  But it’s typically transparent."

You know when there’s an early-bird special, or a discount for using a loyalty card. The price is right there on the shelf, or in an ad, or on the menu.

"Online stores aren't like physical stores," says Internet policy consultant David Robinson. "It's not just one set of offers, and everybody sees the same store. When you're on the Internet, it could be a totally different store."

And how would you ever know? The Northeastern University researchers ran tests that no home user could ever replicate, and came back with only partial results. They recruited hundreds of people online to run an initial round of tests, then created fake accounts in order to isolate variables.  The initial tests showed that Sears sometimes offered the same item for different prices, but the "lab" tests couldn't isolate a variable that triggered a different price.  

This study didn't even test Amazon. With so many different merchants selling on that site, it would have been hard to differentiate offers by Amazon itself from offers by other retailers. 

"One of the problems with the capability of a company to personalize the terms on which is offers you services and the price is this information asymmetry. You don’t know when they’re doing it," says Ryan Calo, a University of Washington law professor who studies privacy rights.

If you’re determined to try to find better prices online, here are some tips.

Be warned: They are not for the instant-gratification-oriented. Effort is involved. So is patience.

 

Follow Dan Weissmann at @danweissmann