4. Gareth Bale
Bale might appear to be a strange inclusion on this list, given that he has just moved clubs for a world-record fee.
However, given the good form he has displayed at the Santiago Bernabeu since arriving in La Liga and the fact that he is still just 24-years-old, it would be somewhat naive to expect him to stay in Spain for the rest of his career.
With Real having lavished £85m upon the Welshman, you can bet that, if they were to sell him in the future, that they would be looking to make a significant profit.