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Would you pay an extra monthly fee just to avoid seeing some online ads based on your web browsing history?

That’s the premise behind a staggered-pricing option offered by AT&T’s ultrafast fiber optic network, called GigaPower, which the company introduced in the Kansas City area on Monday.

For more than a year, the company has offered lower prices to GigaPower customers who are willing to participate in AT&T Internet Preferences, an analytics program that allows the Internet service provider to use information about the sites its customers visit and the search terms they enter for the purpose of personalizing ads to them online or via email or direct mail.

“For example,” AT&T explains on its site, “if you search for a car online, you may receive an email notifying you of a local dealership’s sale.”

For customers who participate in the targeted-advertising program, AT&T has “premier offer” prices for Internet speeds of up to one gigabit per second starting at $70 a month.

In a statement on Wednesday evening, Gretchen Schultz, an AT&T spokeswoman, said that the company was offering its customers “a clear choice” and that the vast majority of them had “elected to opt in to the ad-supported model.”

For customers who opt out of the targeted ads, prices start nearly $30 higher, at $99 a month. The Wall Street Journal reported about the extra cost on Wednesday.

The higher-priced option may not provide more privacy, however. AT&T may still collect information about customers’ Internet usage — whether or not they participate in its ad-targeting program.

“When customers choose not to opt in to the premier offer, they will not receive individually tailored advertising,” Ms. Schultz said in an email. “As described in our privacy policy, AT&T may continue to collect web browsing information for limited purposes such as network management.”

Some privacy advocates took umbrage at the practice.

“They are ensuring that no one chooses that option because it costs so much more,” said Jonathan Mayer, a lawyer and computer science graduate student at Stanford University, who has studied online tracking technology. “And, oh, by the way, it’s not really privacy — given that they are still collecting information about your web browsing.”

Moreover, he said, regardless of whether customers pay to stay out of the AT&T program, advertising networks and consumer-profiling companies could still deliver tailored ads by placing bits of tracking code, called cookies, on customers’ Internet browsers.

By charging its customers more to opt out of having their browsing information used for personalized ads, AT&T seems like something of an outlier.

CenturyLink, one of the largest Internet providers in the United States, for instance, “does not enable online advertising to be targeted to our customers based on their web browsing history,” the company’s website says.

CenturyLink does have a program for its high-speed-Internet customers that allows ads to be tailored to their general locations. But customers can disable the service — apparently without facing higher fees.