The pop superstar was spotted in Kansas City on Monday, cheering on the Chiefs and tight end Travis Kelce, who sparked rumors in July that the two were dating on the podcast he cohosts with his brother, Philadelphia Eagles star Jason Kelce. The rumors went into overdrive as fans realized Swift was sitting in the family box alongside the Kelces’ mother.

Swift’s in-person presence has already boosted Travis Kelce’s jersey sales by nearly 400%, according to one of the biggest sports retailers, and the NFL itself has made clear it’s grateful for the attention. The league edited its bio on X, the social media platform formerly known as Twitter, to read “NFL (Taylor’s Version)” and changed its banner photo to one of Swift clad in Chiefs gear at Sunday night’s game.

“On Sunday, Travis Kelce was one of the top five selling NFL players and saw a nearly 400% spike in sales throughout the Fanatics network of sites, including NFLShop.com,” a spokesperson for Fanatics, the NFL’s official e-commerce partner, told Fortune in an email on Tuesday.

For the $12 billion NFL, Swift’s presence this early in the 18-week season could mean a whole new, powerful fan base: the Swifties.

‘Anything she touches turns to gold’

Swifties—the singer’s legion of fans—can seemingly go to no end for her. For instance, some have dished out up to $20,000 in quests to attend her record-breaking Eras Tour as many times as possible. Sunday’s showstopping cameo has Swifties familiarizing themselves with the rules of football, with some fans claiming on social media that Swift is so big she put Kelce on the map. (The trend is, of course, a joke meant to infuriate football fans—Kelce has won two Super Bowls with the Chiefs, where he plays a leading role as one of the best tight ends in the game today, and potentially of all time. He also hosted Saturday Night Live in May.)

One fan told Today that she was willing to fly to an NFL game just to catch a glimpse of Swift, adding, “She’s going to bring so many people to Chiefs games… Anything she touches turns to gold.”

The massive economic power of the “Bad Blood” singer is no laughing matter: It’s even drawn the attention of the Federal Reserve. In a July report, the government agency credited her tour’s stop in Philadelphia for supercharging the city’s tourism revenue. Analysts coined a phrase for the revenue bump she was giving the cities she visited: the TSwift Lift.

Consider this: Swift makes roughly the same amount in one night from an Eras show as Kelce does in his entire season. During the U.S. leg of her tour, Swift made over $13 million in ticket sales each night. In comparison, Kelce makes roughly $14 million a year.

Swift’s influence even extended to the Google antitrust lawsuit case on Thursday, when the judge joked about whether any internet search could answer the burning question on everyone’s mind that week: Are Swift and Kelce actually dating?

The Eras Tour, which kicked off in March and is scheduled to run through November of next year, is in the running against Beyoncé’s Renaissance Tour to become the highest-grossing of all time. Elton John currently holds that title with his Farewell Yellow Brick Road Tour, which ended in July, making over $930 million. Swift is expected to gross over $1 billion in ticket sales, not to mention the movie of the Eras Tour soon to hit theaters.