Cristiano Ronaldo's agent Jorge Mendes believes several clubs would be ready to pay €300 million for the attacker if Real Madrid were to sell him.
The Portugal international was named the best player in the world for the third time in his career at the Fifa Ballon d'Or gala earlier this year and has been in exceptional scoring form for the current Liga leaders so far in the current campaign.
Ronaldo's representative does not think any club would be willing to meet his buyout clause of €1 billion, but is confident teams would be willing to pay three times the value of Gareth Bale's current world-record fee of €100m - although he expects the 29-year-old to stay put.
"He's the most expensive player ever in the world, because Ronaldo is the best player ever in the world, the best sportsman ever," Mendes told BBC Radio 4. "You can't compare him to anyone.
"A €1 billion transfer is impossible, but if for any reason the club decide to sell him for €300m, someone will pay.
"He loves the Man United supporters, he told me, he started there, but he will not leave Real Madrid."
Ronaldo has a contract with Real Madrid until June 2018.