You and your neighbour add the same packet of coffee to your basket, on the same site, on the same day. You pay 4.99 euros. They pay 3.99.
Nobody warned you. An algorithm simply estimated, from what it knows about you, that you would pay more without noticing.
This is what researchers call "surveillance pricing". And AI could make it far more common.
Dynamic pricing or personalised pricing?
Two things need to be distinguished.
Dynamic pricing changes with market conditions: a train ticket costs more on a Friday evening, a hotel room costs more during a festival. Everyone pays the same price at the same time.
Personalised pricing changes from person to person. It no longer depends on supply and demand, but on what the seller knows about you: your city, your purchase history, the device you are using, the way you browse. The aim is to estimate how much you are prepared to pay.
With AI, which can combine thousands of pieces of information about each customer, the line between the two is becoming increasingly thin.
What is already happening
In the United States, the consumer protection authority, the FTC, has been investigating these practices since 2024. It found that intermediaries were offering retailers the ability to adjust their prices using data as varied as precise location, browsing history or even mouse movements. It now proposes to require retailers to disclose such personalised prices. Its chair summed it up: when you see a displayed price, you expect it to be the same for everyone.
Investigations by the American consumer association Consumer Reports have also found price differences for identical products on the grocery platform Instacart, which disputes those findings and has ended its AI pricing tests. Several US states have begun to regulate, or even ban, these practices.
Since May 2022, a European consumer protection rule, applied in France, requires online retailers to inform you when the price offered to you has been personalised on the basis of automated processing. In other words, a personalised price is not forbidden as such, but it cannot be hidden. If you discover that a site personalises its prices without saying so, you can report it.
How to protect yourself
Compare under different conditions. Look at the same product while logged out of your account, in a private browsing window, or on another device. If the price changes, ask yourself some questions.
Use comparison sites. They show prices from several sellers at once, which makes the differences more visible.
Be wary of loyalty programmes. The discounts they offer are real, but they are traded for data about your habits. That same data can be used to adjust your prices.
Read the small print. Look for mention of a personalised price, which is mandatory in Europe.
Report abuses. In France, the SignalConso platform lets you report a dubious commercial practice. We have listed all the possible remedies when an AI causes you harm.
What to take away
The displayed price was long the same for everyone. It was so obvious that we no longer even thought about it.
AI makes possible a world where each person pays a different price, set by an algorithm that knows a great deal about them. It is not yet the norm, but it is technically within reach. All the more reason to keep your eyes open. And to ask what, at bottom, a fair price is.