The world's two richest clubs by income again spent big, with Barca's signings including Uruguay striker Luis Suarez for 81.25 million euros (107 million US dollars) and Croatia midfielder Ivan Rakitic for around 20 million.
Real lured Colombia playmaker James Rodriguez to the Spanish capital for around 80 million euros and snapped up Germany midfielder Toni Kroos for 30 million, seduced by the pair's success at the World Cup finals in Brazil.
However, while Barca are widely perceived to have improved their squad as they look to bounce back from a season without major silverware, critics have suggested European champions Real will be significantly weakened by the exit of midfielders Xabi Alonso and Angel Di Maria, sold to Bayern Munich and Manchester United respectively.
The sense of unease was heightened on Monday when dressing-room heavyweight Cristiano Ronaldo, Real's top scorer and current World Player of the Year, appeared to criticise Perez's transfer policies.
The construction magnate has spent hundreds of millions of euros of the club's money on the top players, with his strategy also driven by how many shirts new recruits will help sell.
Alarm bells rang at the club when they let slip a two-goal lead to crash to a 4-2 defeat at Real Sociedad in La Liga on Sunday, when Ronaldo was sidelined by injury.
"I have a very clear opinion but I cannot always say what I think," the Portugal forward told reporters when asked about his club's recent transfer dealings.
"If not I would be on the front page of the newspaper tomorrow and I don't want that. But, if I was in charge, maybe I would not have done it like that.
"But if the president thinks that the best thing for the team is to buy the players he bought and let others leave we have to respect and support his decisions."
Ronaldo's comments, together with grumbling from coach Carlo Ancelotti, will be uncomfortable for Perez and stand in stark contrast to the upbeat tone of a news conference given by Barca sporting director Andoni Zubizarreta on Tuesday.
Spanish sports dailies Marca and As both splashed Ronaldo's remarks across their front pages, while Real's Spain contingent were quizzed about the situation when they met up with their international team mates.
"Everyone has their opinion and it is respectable, I am not going to make any comment about Cristiano or any player," centre back Sergio Ramos, one of Real's captains, told reporters.
"We belong to the club and we must respect the rules of the club," he added. "I am not going to reveal my opinion, it's not the time to be drawing conclusions."
Barca's hand was forced in the market after the club were given a temporary reprieve from a transfer ban for breaching rules on the transfer of under-18 players while an appeal to soccer's world governing body FIFA was ongoing.
They lost the appeal and may not be allowed to buy again in the next two transfer windows but have added Suarez and Rakitic, as well as centre backs Thomas Vermaelen and Jeremy Mathieu, goalkeepers Claudio Bravo and Marc-Andre Ter Stegen and fullback Douglas to their ranks.
They have begun the La Liga campaign in confident fashion and are the only side to have won their opening two games as they seek to improve on last term's second-place finish.
Zubizarreta said he was delighted with the squad and predicted Barca would be a major force under new coach Luis Enrique, who has replaced the discarded Gerardo Martino.
"We again have a team that is at a very high competitive level," former Barca and Spain goalkeeper Zubizarreta told reporters. "I am very pleased and we will see how far we can go."
Champions Atletico Madrid are again expected to mount a realistic challenge after some astute business in the transfer market when they bought in the likes of Croatia striker Mario Mandzukic, France forward Antoine Griezmann and Italy winger Alessio Cerci.
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