The 27-year-old Spain international is reported to be keen on a move back to his homeland, but the Reds are holding out for a fee of around £30million.
Perez told the Daily Telegraph: "Some people obviously thought that because we said we wanted more Spanish players, they could ask for fees which don't correspond to reality.
"A year ago certain players we've asked about would have cost less than half the price we're being quoted now.
"If necessary, we'll find the Spanish players we would like for the squad in our youth system."
Of probable departures from the Bernabeu, Perez added in AS: "We made strategic signings very quickly and that meant that we suddenly had a huge number of players with 29 here.
"We are trying to find other teams for those players who will not play a lot for us, but we have not yet managed to do that.
"For any more players to come then some will have to leave."