Kaka, whose switch to the Bernabeu eclipses Real's £47m capture of French midfielder Zinedine Zidane in 2001, also revealed he sought the advice of ex-Milan team-mate David Beckham before committing to the move.
He added: "I spoke to some friends, like Beckham, who has already played for Real. He said it's a fantastic place to play. I spoke to him this past week and he kept helping me, he said I made a positive choice for my career.
"I'm not going to Real for money, as I had other offers. But I knew I would only leave Milan to play for Real."
Perez expects more high-profile new arrivals at the Bernabeu before the start of the new season and Ronaldo is now his main priority.
He told Radio Marca: "This is only the beginning. The fans want us to bring in Ronaldo and I'm going to do everything to make it happen."