Kristen Schwab

In fact, it's been around in some form as long as commerce has.

Joseph Turow is author of The Voice Catchers, How Marketers Listen In to Exploit Your Emotions, Your Privacy, and Your Wallet.

He says shopkeepers would game out what customers were willing to pay.

Characteristics like what kind of clothes you wore or who your friends and family were.

The difference, though, is before, a business owner had to guess if a woman's baby bump was indeed a baby bump.

Now a retailer knows the instant she adds prenatal vitamins to her cart.

He says a lot of consumers have no idea surveillance pricing is happening.

Instacart recently ended a pilot that allowed retailers to charge different prices for people living in the same city.

How common this kind of practice is, no one really knows.

But Sheikha Jain, a retail partner at the consulting company Simon Kutcher, says retailers are watching us closely.

Often, retailers are using that info technically not for surveillance pricing, but surveillance discounting.

Here's a coupon for being a member or 10% off that immersion blender sitting in your cart.

It's why, as a consumer, it is more difficult than ever to figure out if you're getting the best price.

Garrett Johnson is a marketing professor at Boston University.

Price discrimination sounds really scary, but effectively it means that it's good for some consumers and not so good for others.

He says if you want to compare prices, you kind of need to hide.

You can open the website in incognito mode using your mobile phone, maybe even turn off your Wi-Fi.

But are we really going to do this dance every time we buy something as mundane as toothpaste?

I decide to shop for toothpaste on Walmart.com on two different browsers.

On one, I'm signed into my account, which has my information.