I think it was just made up by the media by saying 400 million I don't think this will happen for the sale of Osimhen because this player is not his level at that price, it also doesn't make sense and who wants to buy him? If you say this is nonsense then I believe it.
Mbappe does have a high value at the moment the contract at 200M is still very possible especially now that Real Madrid is still eyeing him until his contract expires. Let's see how Real Madrid make a special offer to Mbappe.
I don't know if the 150M for Osimhen will go to Chelsea this is just a rumor while Real Madrid will not prioritize the Napoli player, while for the Arab club Osimhen there is no interest there.
A few minutes ago I saw on social media that Osimhen would stay at Napoli. Osimhen will extend his contract until 2026. In the contract there is a release clause of around €130 million. Napoli's clever move, but I don't know how much Osimhen's new contract is worth at Napoli. Actually, Osimhen sat has decreased. The statistics with last season are very much different. It would probably be Napoli's gamble if no team wanted to buy him because of the calusal release which was quite expensive.