The Spanish press has reported that 'Los Blancos' could pay up to 120million euros in order to secure the services of the 2013 PFA and Football Writers' Player of the Year, while coach Carlo Ancelotti has admitted the club "are trying to find a solution to the situation", in reference to the signing.
During an interview with ESPN, Perez hinted that Madrid might be trying to lower the price for the Tottenham star but refused to speak at length about the deal.
He said: "We don't usually talk about players out of respect to the player, the club and their chairman, with whom I enjoy a good friendship after signing (Luka) Modric last season. And as I don't talk about players, I don't talk about transfer fees either.
"However, of course, 100million euros seems to me like a lot of money, all things considered. But I won't talk about players or money, because I shouldn't and I cannot."
The president explained that the club were still trying to tie Cristiano Ronaldo down to a new contract, as his current deal expires in 2015, and expressed confidence in securing the player's future at Madrid shortly.
He said: "We are all convinced he is going to finish his career at Real Madrid. At the end of the summer we will try to resolve this situation. I believe this will happen before the end of the month, or at the start of next month.
"We are not in any hurry, because both parties have the same will. We will resolve it satisfactorily. At least that is what I want, and I believe it's what he wants too."
On Wednesday, Madrid beat their former coach Jose Mourinho's Chelsea 3-1 in the Guinness International Champions Cup in Miami, little over two months after the Portuguese left the Bernabeu following a trophyless season that was overshadowed by tension between the coach and some of his players.
Perez insisted that Mourinho helped the club take "a competitive leap" in his three years at Madrid, but also tried to explain what went wrong in his last season.
"Last season we made a bad start and that conditioned most of the season," he said.
"At Madrid there is always something going on, because everything gets magnified, that's part of our history and what makes our club so great.
"You have to know how to handle that pressure. Everyone feels it, the players, the coach and the president, the only difference is I have more experience.
"People that come here for the first time don't consider it normal, but those who have known the club for a long time know that the pressure here is what has made Madrid the biggest club in the world."