A shopping cart on the Old Navy website containing socks, leggings, a T-shirt, and jeans changed price three times during a two-week period. The total price of the tracked cart dropped by $11, a decrease of nearly 17% from its starting price, during the experiment.

In two in-person visits to Old Navy stores, the prices of the same items were higher than the prices in the app cart.

The pricing fluctuations reflect broader changes in retail pricing strategies. Retailers including Walmart and Kroger use digital price tags that adjust prices in real time. Price discrimination is the practice of charging different prices to different buyers for the same product.

"Both the non-student and student are getting the same product — a movie ticket — but the student is paying less," said Mark Tremblay, assistant economics professor at the University of Nevada, Las Vegas. "Students generally have less money. Offering a discount attracts students who might not see the movie otherwise, and the theater makes money."

Richard Dickson, CEO of Gap Inc., which owns Old Navy, described the company's evolving approach to promotions. "How we promote is a much more refined and directed narrative," Dickson said.

"You just have these constant price fluctuations, and that's how things will be moving forward," Tremblay said.

The National Retail Federation states that digital pricing can result in lower prices during off-peak periods and more tailored discounts.

"This ain't your momma's home economics, right? Everything we learned about shopping as a kiddo or everything that you've understood about shopping for decades has shifted into your feed. And comparison shopping is really difficult now because there often isn't a posted price, or the posted price is varying minute by minute, or day by day," said Lindsay Owens, executive director of the Groundwork Collaborative.