The mismatch in performance and market value is because Osimhen is outside the European League but if he were in a European club his market value would certainly be high. Now Osimhen must return to Europe and no matter which club he will stop by later, what is clear is that Osimhen career needs to be fought for. Next season is the right time for him to go and accept the challenge in the European championship. If it continues to be postponed there will be no more opportunity to raise his name, Osimhen must realize that the real competition is in Europe.
Last I checked Osimhen is still in Europe. He plays for Galatasaray in Turkey and he's performing very well there. He's among the top scorers in the league and he's on course to help them win the league for them. He's not in Europe's top 5 leagues but he's still in Europe and still has a contract with Napoli.
I think it's a good thing his market value dropped so it will be easier for the team to sign him. Chelsea are feeling the consequences of not signing Osimhen last summer. I belive other top clubs will go for Osimhen or even Chelsea might go back for him.