Ronaldo rewrote the history books during his nine-year stay in the Spanish capital, ending his time at the Bernabeu as Madrid's leading all-time scorer with 450 goals in just 438 games.
However, he joined Italian giants Juventus in a deal worth almost £100m during the summer, and Perez admitted that the nine-figure sum was too good to turn down.
"The most expensive sale this year has been Cristiano," the Madrid president told reporters.
"When we all believe that the best thing is this that has happened, we reach an agreement. At Madrid nobody gave more than €100m.
"He wanted to go by subjects people and the most that has gone has been for that amount, we have not had many more offers."
Ronaldo has since scored two goals in his first five appearances for Juventus, and was sent off on his Champions League debut for the club on Wednesday night.