I wonder why Napoli is bent on keeping Victor Osimhen instead allowing him to play for a team like Galatasaray that is still showing interest in the player and ready to pay the amount they have offered
To be fair, it's just a business deal in the end. If you know your product is rated so highly and someone is in dire need of it, you can demand more money for it. Whether they demand too much that it pushes away the buyer is another question, though, and only the result of the negotiation table can answer that. I don't think professional players don't know that, as much as the club PR talks about being a family or something along those lines.
Yes, that's a very good example. It's akin to supply and demand. Galatasaray got a lot out of him last year, and he played really well for Galatasaray. Napoli knows how much the team wants him. That's why Napoli is trying to force Galatasaray to do what they want. Galatasaray, in turn, wants him so badly. That's why there are transfer disagreements. I don't know if a team from another country, like La Liga or Italy, would be as strict about signing him. I could interpret this as Napoli trying to make more money.