The return of mega-concerts since the Covid-19 pandemic, with Taylor Swift and Beyoncé leading the way, has highlighted the lucrative links between fashion brands and pop stars.

Stage costumes have long been a way for designers to gain massive exposure – think of Madonna's cone bra that helped make French designer Jean Paul Gaultier a household name in the early 1990s.

From Edith Piaf's little black dress to Elton John's whacky glasses to David Bowie's many elaborate fashion statements – music stars have often communicated with their clothes.

A pop star endorsement can have an immediate impact on a brand's bottom line.

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Sales of rhinestone cowboy hats increased by more than 1,600% after Beyoncé wore one for her Renaissance tour, according to the Klarna payment platform.

Data specialists Launchmetrics estimated that Alexander McQueen saw a $7.7 million boost for dressing Beyoncé, while Versace sales jumped $6.3 million thanks to Swift.

Designer David Koma told Vogue that one of his dresses sold out within a day after being worn by Beyoncé, and he saw a 53% increase in his Instagram followers within a month.

Dsquared2 designers Dean and Dan Caten, who have also dressed Queen Bey, told the magazine, "For us, the objective is not really about sales but about image and the exposure that comes from aligning with a major artist that looks good in our clothes and fits our aesthetic."

Swift goes through an average of 13 outfits each night of her Eras Tour, whose European leg kicked off in Paris on Thursday.

These include ball gowns for the country section, sequined ensembles for the pop hits, and vaporous dresses for her forays into folk.

They are courtesy of high-fashion labels like Cavalli, Louboutin, and Versace – though she was not always an obvious fit for them.

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"Luxury designers wouldn't have been as interested in partnering with Taylor because her presentation as a pop star was down-to-earth, unlike someone like Beyoncé or Lady Gaga," said Satu Hameenaho-Fox, author of Into the Taylor-Verse.

"But the level of her fame is so extreme now, and she's become viewed as very much in the pantheon of Great American songwriters, that – without ever being daring in her fashion – she's considered almost an institution, a classy institution that any brand would benefit from being associated with."

Like everything else to do with Swift, her fans dissect every outfit for coded messages.

Swifties were eager to see how she presented songs off her new album, The Tortured Poets Department, which got its first live performances in Paris.

The 34-year-old singer adopts a Victorian gothic aesthetic in the album artwork.

Intriguingly for many Swifties, in the video for new song Fortnight, she wears outfits by young US designer Elena Velez, who has stoked controversy with provocative "post-woke" stunts.

"Does that mean that Taylor is moving into a more kind of controversial figure space," wondered Glenys Johnson, author of Taylor Swift: The Story of a Fashion Legend.

"The lyrics from her latest album were a lot about wanting to move beyond the good-girl image she has. We Swifties are eager to see if this means Taylor evolves into a more controversial figure," Johnson added.

On opening night in Paris, Swift debuted a seven-song set inspired by her 11th studio album, performing in a white gown, similar to the one from the Fortnight video but hiked up in the front, illustrated with lyrics from the song in cursive.