The January transfer window is supposedly a market for desperate buyers but Barcelona sit five points clear at the top of La Liga and have made more signings than any other team in the division.

On Monday, it was Kevin-Prince Boateng doing kick-ups at the Camp Nou and three days later came Frenkie de Jong, the 21-year-old Dutch midfielder for whom Barca will pay Ajax 75 million euros ($85 million), with a further 11 million euros due in add-ons.

"In De Jong, we add talent, youth and a player with Barca style," said president Josep Maria Bartomeu. "He will be a key player in the next few years."

Boateng and De Jong, who will join in July, follow Jeison Murillo from Valencia, a central defender for the present, and Jean-Clair Todibo from Toulouse, another to mould for the future, who will also arrive in the summer.

Barcelona go up against Catalan neighbours Girona on Sunday and a few hours later, less than 70 miles away, Real Madrid play Espanyol.

Madrid's most expensive player will be Vinicius Junior, the 18-year-old signed for 45 million euros last summer. Gareth Bale, who is injured, is the only one more costly and they signed him six years ago.

Since then, the European champions have spent more than 50 million euros just once, on James Rodriguez, who is now on loan at Bayern Munich and not expected to return.

Barca have smashed that total five times in the same period, twice more than doubling it, to bring in Philippe Coutinho and Ousmane Dembele.

Those deals were propped up by the sale of Neymar, which helped the club announce record revenues of 914 million euros for last season. They predict another jump to 960 million this term.

But Real's finances are also in good shape. They expect to report figures of 752 million euros for 2018-19, with their president Florentino Perez confident his club can be the first to reach a billion.

"The only way to remain independent is to be financially healthy," Perez said in September. "That is the base of our sporting success."

Perhaps Madrid's reduced transfer spending is due to planned improvements to their Santiago Bernabeu home, for which a 575 million euro loan will be taken out. But Perez has insisted it will not impact the team, while Barcelona are also upgrading the Camp Nou, at a cost of 400 million euros.

Perez could instead be keeping his pockets full for a fresh tilt at Neymar next summer, with the Brazilian's future at Paris Saint-Germain seemingly uncertain.

Neymar would be the kind of star name to fill the void left by Cristiano Ronaldo and there would be added satisfaction in bringing back the player that trained at Valdebebas as a 14-year-old, only to sign for Barcelona when he was 21.

In recent years, Madrid's strategy has been to target youth. "We are strengthening our search for young players that will become the next great players of the sport," Perez said in July.

But, despite their historic success in Europe, Barca's splurge must make them nervous.

Key players have shows signs of age or left, Neymar remains at Paris Saint-Germain and the Catalans are 10 points ahead, firmly on course to win their eighth La Liga title in 11 seasons.

"We have to get closer to the top," coach Santiago Solari said on Thursday.

Madrid could save face by winning the Champions League again but the task will be harder this year without Ronaldo, who scored 15 goals en route to them hoisting the trophy in May. Perez also failed to replace him last summer.

Atletico Madrid, Barca's closest challengers, are expected to complete a deal for Chelsea's Alvaro Morata this month but not before Saturday's game at home to Getafe. Sevilla, in fourth, play at home to Levante.