There was plenty of excitement when Manchester United signed Anthony Martial from Monaco back in 2015. At the time, United were sure that they had acquired one of the future golden boys of world football, having forked out around a reported price of £36 million.
However, the price could have escalated into much more than that. Having competed with several clubs for Martial's signature, United reportedly included three clauses into the Frenchman's contract that amounted to £21.6m in performance-related add-ons.
Each of the clauses worth £7.2m, going to Monaco immediately when triggered — who were confident that they'd all materialise.
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