Cristiano Ronaldo, Lionel Messi and the world's top footballers may earn huge salaries but the sums they make from boot deals can be equally astounding.
In July 2017, the new face of French football, Kylian Mbappe, pursued by Europe's elite clubs, caused a frenzy of excitement after tweeting he had a big announcement to make. People thought he was going to announce his move to Real Madrid or Paris Saint-Germain.
However, the 19-year-old actually announced that he was extending a deal he signed with Nike when he was 13.
Within weeks he had moved on loan from Monaco to PSG, who are also sponsored by Nike.
It's not just a case of lacing up the customized boots and picking up the fat cheques, yet, the high earners are brand ambassadors and have stringent public relations commitments.
Image rights specialist Frank Hocquemiller explained: “It's not like having a job and being an employee working for an employer. If you have signed a deal with Adidas, Nike or Puma, it means they have bought your image rights. It comes with a certain amount of public relations requirements and social network management.”
Kevin Geoffroy from Footpack.fr, a sportswear news site, said: “The sportswear companies are investing more and more money and they want a return.”
So Twitter, Instagram or Snapchat accounts of the stars are harnessed by the sportswear giants to push their product.
Arsenal and Germany midfielder Mesut Ozil recently advertised Adidas on his Instagram account, where he pointed out he had a paid relationship with the German brand. That pay is reportedly in the region of £3.7 million (4.19 million euros) a year.
Most top players have similar deals. According to reports, France and Manchester United midfielder Paul Pogba recently signing a multi-year deal with Adidas worth 40 million euros.
David Beckham retired in 2013, but continues to plug Adidas products and his celebrity lifestyle plays perfectly into the current sportswear trends. So out with the football boots, in with the black Adidas tracksuits for the arrival lounge at Los Angeles' LAX airport.
No need to guess that Real Madrid's Ronaldo enjoys the most lucrative football boot deal in history, with his contract with Nike thought to be worth £6.2 million a year.
To give an idea of the bidding war that pushes up the value of these contracts, current Nice and former Manchester City and Liverpool striker Mario Balotelli signed with Puma ahead of the 2014 World Cup for a rumored £5.1 million per year. The Italian's career has had so many stops and starts since then, it is doubtful he still earns anywhere near that sum.
Using footballers to promote products is nothing new. In the 1930s Andre Abegglen, the Swiss center-forward at French club Sochaux, launched his own footwear brand with the slogan: "For a good worker, good tools, to a good footballer, good boots."
There have always been clashes of interest too. Dutch great Johan Cruyff would only play for his national side if they took off one of the three Adidas stripes from his shirt as he had signed with French brand Le Coq Sportif.
He would later sign with Puma, and picked up one of his Ballon d'Or awards with the brand's logo emblazoned on the pocket of his dinner jacket.
In France's 1998 World Cup win, Coach Aime Jacquet narrowly avoided a players' strike from disgruntled players baulking at wearing Adidas boots for the national team because of their own private deals.
The players won that World Cup wearing Adidas, but ever since they have been able to wear what they want.
Another anecdote from the France set-up suggests however that for the 2014 official World Cup team photo, regardless of height, only players wearing Nike boots were allowed to sit in the front row because Les Bleus' shirts are made by the US giant.