Here, we look at some other costly teens:

WAYNE ROONEY
Became the world's most expensive teenager when he moved from Everton to Manchester United for £27million as a 19-year-old.

SERGIO RAMOS
Real Madrid paid £18.5million for the Sevilla defender in 2005, making the Spanish international the second most expensive teenager behind Rooney.

MIKEL JOHN OBI
Chelsea agreed to pay £4million to Norwegian club Lyn Oslo and £12million to Manchester United, the latter to waive any rights to the 19-year-old after a protracted transfer row. And the towering midfielder has so far shown signs of being a sound investment.

THEO WALCOTT
Arsenal paid Southampton £5million in March last year on his 17th birthday, in a deal which could eventually be worth £12million. After his unfortunate World Cup, when he was an unused substitute, Walcott broke into the Gunners team last season.

LIONEL MESSI
The 18-year-old Argentina forward joined Barcelona aged just 13 and has made a name for himself in the last two years to establish himself as one of the world's finest talents. Has an incredible £100million buy-out clause in his nine-year contract.

SERGIO AGUERO
Atletico Madrid last summer splashed out a fee reported to be in the region of £15.7million for the 17-year-old Argentinian from Independiente. Dubbed the new Messi, he has endured mixed fortunes this season.

CRISTIANO RONALDO
Cost Manchester United £12.3million when he swapped Sporting Lisbon for Old Trafford in 2003 as an 18-year-old.