8. Cristiano Ronaldo
Why isn't Cristiano Ronaldo higher on this list, I hear you cry.
Well, remember that the Portuguese superstar turns 30 in less than a years' time - and then consider that fact that he is indispensable to Real Madrid, who handed him a new long-term contract last September.
Even if he doesn't stay at the Bernabeu until 2018, no club will be prepared to pay more than £86m for a player in their early thirties.