Gavi could be a very good investment. He is still very young and very talented, his price is not too high and he has great potential. But would a team like Barcelona, which is young and preparing for the coming years, let Gavi go? I don't think so. Recruiting young talents between 20-24 years old is the biggest goal of almost all teams right now.
Van Dijk is very talented of course, but don't you think he's a bit old? He can play well for 1-2 more years at most, Then he will get weaker and weaker

Even though PSG meets Gavi's release clause, I don't think Hansi Flick will allow Gavi to join PSG because Gavi is a talented player who will help Barcelona in the long run, and Hansi Flick won't want to lose a player like Gavi from his squad because he's still in the process of rebuilding the Barcelona squad.
In last few years many things happen which was not expected to happen because there is always room for changes and personal decisions so Gavi to PSG is also not easy to predict because everything is possible Gavi feeling not comfortable due to some internal issues with coach and sporting director.
Even situation is still not clear, and they are creating middle room, but media sparks some debate about this which is interesting for all to give their own views after winning Champions Trophy now PSG is completely different club and many players surely want to have place here but Gavi is surely big talent. Hansi Flick is strengthening Barcelona so it's not going to happen easily but if Gavi will be not comfortable then surely things can go either way because players like or dislike is always important in all big decisions.