Madrid have long been linked with a move for the Portugal international and, despite last month's denial, there continues to be speculation that they already have a deal in place for the 24-year-old.
"I don't know anything about the story of Cristiano Ronaldo. I only just took charge," he told television programme '59 segundos'. "But what I am sure of is that which seems expensive is the cheapest."
He added: "In my last era the cheapest was (Zinedine) Zidane, who seemed very expensive because we paid 73 million (euros) for him.
"Without knowing who we can get, there will be a massive effort for the great players of the world, because that is the Real Madrid model."
Perez laughed off suggestions that Ronaldo's fierce temper could hinder him at the Bernabeu.
"I have not seen anything about him that would prohibit him from playing at Real Madrid," he added. "I have seen him get angry because he wants to win and (because of) his competitive spirit.
"The information I have on him says that he is an example on the pitch, a model."