The cool thing to wear to the big game? Something old.

The Team Store: A glorified souvenir shop in stadiums and arenas, where sports fans purchase official jerseys, snapback hats and a variety of magnets and key chains.

Also: quite passé.

“That's really weird,” says Lily Shimbashi Sporty, a pop culture newsletter and podcast aimed at female sports fans. “No one buys clothing from the teams anymore, because it is boring. It's ugly.”

For more and more fans, official competition clothing has been replaced by less official, trendy equipment sold online. This shift has created a particular frenzy around vintage sportswear, such as graphic T-shirts circa 2001 – the Mets opening day or Florida A&M University homecoming – or colorful, crunchy NBA Starter jackets.

According to GoogleTrends look for interest vintage NFL items have nearly quadrupled in the past year, especially in Missouri, home of the Kansas City Chiefs. The day after it was determined that Kansas City would play the San Francisco 49ers in the Super Bowl, eBay searches for vintage 49ers T-shirts increased by more than 400 percent in the United States and Canada.

But this isn't just about the Super Bowl: In the last six months, searches on Etsy for vintage football jerseys, regardless of team, are up 62 percent, compared to the same period last year.

“People want to wear something unique,” ​​says Michael Spitz, owner of Mr. Throwback Vintage, a store in the East Village that specializes in sporting goods from the 1990s. “They don't want to wear current clothes that anyone can buy in a sports store or stadium.”

Mr. Spitz, a collector of basketball jerseys, has been active in New York for more than 11 years. “Every year it has become more and more difficult to obtain vintage sportswear,” he says.

At Westside Storey in Kansas City, vintage Chiefs sweatshirts cost about $25 when owner Chris Harrington added them to his inventory six years ago, he said. Today, some of his sweatshirts sell for more than $300.

Explaining this inflation, Mr Harrington said the team has improved significantly, increasing demand while supply has decreased. To begin with, there wasn't much on offer. Much of today's popular vintage sportswear comes from the '80s and '90s. And at the time, Mr. Harrington said, the Kansas City team didn't make much merchandise and targeted a smaller market compared to the New York Giants or Jets.

The vintage clothing business has also become more competitive, in every category from concert T-shirts to red carpet looks. When it comes to team merchandise, there's also a plethora of “vintage-inspired” T-shirts and “retro” sweatshirts – imitations and counterfeits – being sold online.

“You can take a label off and wash it a few times, and 75 percent of people who aren't familiar with vintage will think it's vintage,” Mr. Harrington said.

Then came Taylor Swift. In December, she wore a Westside Storey sweatshirt while cheering on her boyfriend Travis Kelce. Half red and half black – a color combination that the average Swiftie could probably work into an album release theory – with large capital letters spread across the chest, the piece cost $250. Naturally made headlines.

Westside Storey is selling its vintage Chiefs apparel online in two-month batches, which are announced on Instagram. Before Taylor (BT), only about 60 percent of a drop would sell out, with each attracting 30 to 50 active visitors to the website, Mr Harrington said.

After Taylor (AT), the drops typically sell out within 10 minutes and have attracted about 1,200 to 1,500 visitors to his site, he said.

At Mr. Spitz's store in the East Village, Ms. Swift also “changed the game and helped increase sales,” he said. “There's always demand for any team in the Super Bowl, but of course there are so many new fans these days because of Taylor Swift.”

Sarah Chapelle, who is a Instagram account dedicated to cataloging and analyzing the pop star's style — a book coming in October — said in an email that Ms. Swift's fans appreciate how her game-day choices “center her excitement and support as an audience member, but don't function as an outright billboard for the latest merchandise.” Ms. Chapelle wrote that the singer chooses “small businesses that are often local to Kansas City, women-owned, handmade or offer sustainable choices like vintage.”

An old sweatshirt can never be just an old sweatshirt to Ms. Swift. It is a statement of values.

While it's true that vintage pieces appeal to young, sustainability-minded consumers, Ms. Shimbashi says, they are also seen by these shoppers as rare and valuable artifacts. That could explain their acceptance of a $200 price tag for a cotton sweatshirt.

“People want to be part of a team's legacy and history in a unique way,” said Ms. Shimbashi.

“If you have a grandpa or grandma who is a sports fanatic and they have something from growing up, you need to get your hands on that,” she said. “That is so valuable right now. I have my dad's leather Knicks jacket from back in the day, and I'll hold onto that forever.