Talking about salaries, maybe this is still related and maybe there are those who don't know that the top salary in La Liga is held by a Barcelona player, not Real Madrid. As you said, De Jong is the player with the highest salary, followed by Lewandowski and even Mbappe, in a team with good finances, can only occupy third place. Management's mistake in agreeing on player salaries at the start of signing resulted in unexpected problems and that is what Barcelona must face now.
The problem of lack of funds each season will continue to haunt Barcelona and because of that, De Jong and Lewandowski are like greedy players who are draining the club's finances. But that also cannot be blamed considering that the contractual agreement that has been made cannot be changed. With this, Barcelona will not easily make a decision to recruit players even if there are players like Nico Williams who only need to agree on a fee. Even if there are loan rumors about Nico Williams, Bilbao will definitely not give him and it is possible that another team could take him before Barcelona.
Real manages their payroll very wisely, they use their authority and find a middle ground so that players want to play in their team and not overpay their salaries. Perhaps Xavi's desire to sell Lewandowski was appropriate, so they could improve the payroll, which was to the benefit of the Barcelona, Lewandowski is no longer as good as before but still receives very big money. In conditions of financial problems, everything matters, and you need to think not only about how to do without new transfers, but also about how to cut costs within the team, including the unreasonably high salaries of top players.