Ronaldo is worth how much?

Portugal's Cristiano Ronaldo will finish his career at Real Madrid. Source: Walter Bieri / AP

CRISTIANO Ronaldo will finish his career at Real Madrid, the Portuguese superstar's agent says, as he put a 300 million ($578 million) price-tag on the world footballer of the year.

"He is the best player ever in the world. You can't compare him with anybody else," agent Jorge Mendes said of Ronaldo in an interview with the BBC.

"If for any reason the club decide to sell him tomorrow for 300 million pounds, someone will pay," Mendes added.

Cristiano Ronaldo of Real Madrid celebrates scoring a goal. Source: Getty Images

But the agent said there was no danger of his 29-year-old compatriot, voted the world's best player for a third time last month — beating Barcelona's Lionel Messi to the award — leaving Real's Bernabeu Stadium.

"Cristano Ronaldo? One billion. His buyout clause (is) one billion, so it is one billion. It is impossible to find someone like him."

Real Madrid's Portuguese forward Cristiano Ronaldo poses with the Ballon d'Or award for player of the year. Source: AFP

Asked if Ronaldo, who joined Real from Manchester United for a then-world record 80 million in 2009, would end his career with the Spanish giants, Mendes said "for sure".

"He will not leave Real Madrid," Mendes insisted.

Cristiano Ronaldo poses in front of a 19m high billboard during the global launch of the CR7 in Spain. Source: Getty Images