From what I know about the Oshimen deal, I think Chelsea can afford to get him from Napoli by paying Napoli's asking price, but the problem has always been about Oshimen's personal wages. We all know that Oshimen deserves more, but I don't think Chelsea is willing to offer anything more than £200M, for a proven striker like him. Let's see how far Chelsea can get in this coming season with Jackson as their top man.
Napoli don't want to see Osimhen leave free next year and they don't need it in the club so the release clause might become lower days before the end of the transfer window.
Osimhen want to return to Serie A, that's why he rejected the very interesting offer of Al-Hilal and presumably Galatasaray, otherwise he didn't say anything about it. Galatasaray needs him and he doesn't want to say anything about that. Otherwise I read that PSG and Juventus are among the teams that could be interesting for him