Though not many of us thinks that Napoli's approach about Victor Osimhen's future is right, but we still have to look things from the club's point of view. They're requesting for huge amount of money before the can let the Nigerian striker leave because they know the quality he posseses as will sign his replacement if he leaves so you should expect them to go for a fee as to make gains with his sale. Paris Saint Germaine couldn't get a single fee when Kylian Mbappe left the club because they rejected every offer that came to their table about the player with the intention of convincing him to extend his contract with the club but Napoli I don't think wants to keep Osimhen which is why they're open to let him go if they receive a good offer.
It was reported yesterday that Paris Saint Germaine are showing interest in Osimhen and are likely to sign him this summer. If the two clubs should come to terms in their negotiation, Osimhen will be joining the French champions

Truly even Napoli seems to be aware that the drop in his performance is due to the fact that he's not perfectly comfortable playing at Napoli again, so if he goes elsewhere especially Chelsea where he's always seen as his dream team, his performance may likely get back top notch and that will mean he was worth every of the money spent on his transfer and so they have decided to make sure to make as much profit as they can off his transfer so it doesn't appear like they lost at any point. Napoli may not suffer the same fate with PSG in the case of mbappe because osimhen still have an unfinished contract and that's why they kept such a high bid on him.