Cristiano Ronaldo would sell for £300m if Real Madrid decided to let him leave tomorrow, the Portuguese superstar's agent has told BBC Sport.
Jorge Mendes said the 29-year-old forward was the "best player ever" and the "best sportsman ever".
Mendes added: "You can't compare him with anybody else."
Ronaldo was voted the world's best player for a third time last month, beating Barcelona rival Lionel Messi to the prestigious award.
Asked how much he was worth, Mendes said: "Cristano Ronaldo? One billion. His buyout clause one billion, so it is one billion.
"If, for any reason, the club decide to sell him tomorrow for 300 million, someone will pay."
However, Mendes insisted his countryman, who cost Real Madrid a world record fee of £80m in 2009, would stay at the Bernabeu, despite his "love" for supporters of former club Manchester United.
"He will not leave Real Madrid," Mendes told BBC sports editor Dan Roan.
Mendes, who is reported to have brokered more than £1bn worth of transfers, has been described as the most powerful figure in the game.
"People have the wrong idea about agents," said Mendes.
"Being an agent means many different things. I'm someone normal, I'm working hard every single day. I have ambitions, determination and being honest, doing the right things... this is most important."
He described football as the "most important sport in the world" and defended the wages players now command, saying they "deserve the maximum possible".
Mendes compared working with his players on contracts as "like a family".
"It is like when you talk with your son, with your family... always to try to find the best way to support them," he said.
Mendes also described the ban on third-party ownership of players as "illegal" and "catastrophic" for clubs.
"Fifa and Uefa are not the police," he said. "I think that's it's very important to establish rules, the right rules, but not to stop it."
Mendes, a former DJ and nightclub owner, also represents Jose Mourinho, Luiz Felipe Scolari, Radamel Falcao, Angel Di Maria, James Rodriguez, David De Gea, Victor Valdes and Diego Costa.