I agree with you. Even though Barcelona has a serious financial crisis, if they sell De Jong and recruit another player with the same quality or more then they will still have to pay the same salary as De Jong receives. I heard news or rumors that said De Jong would be sold because the club management planned to recruit Bernardo Silva from City. I think De Jong is a good player but unfortunately he often suffers from injuries so his performance is not optimal. This is similar to Dembele before, where Dembele often suffered injuries at Barcelona but strangely he became a quite strong player at PSG.
De Jong should definitely be kept by Barcelona. I believe he is one of the really skilled midfielders in the world now. He has been a consistent player since he joined Barcelona as well. As long as Barcelona doesn't manage to find a talent similar to him and much cheaper too, it isn't reasonable to sell him.
Bernardo Silva transfer would probably fail. He has renewed his contract until 2026 and he is happy at Manchester City.Barcelona finances have been a meme topic recently.
After they signed Hansi Flick there was a meme created like they couldn't arrange a car for him that he had to go to the team facilities by bus. 
I hope Barcelona solves the existing financial problems to strengthen the squad more. Otherwise it is hard to compete with Real Madrid.