Osimhen's contract ends in the summer of 2026, so no one will pay 75 million for one year, situations like what happened when Bayern bought Kane or Barcelona Lewandowski (both had to play out another year of their contract) do not happen that often. And as I already wrote, it seems to me that Osimhen is simply trying to upset Napoli - he wants to get his entire salary (most of which is paid by Napoli even when he is on loan) and leave for free.
This oshimen and Napoli issues has been going on for too long if Napoli doesn't want him to play they should allow him to go I think that the problem is from both parties because from what I see both parties don't want to change grounds on where they are standing compromise should be taken for any good thing to happen if not I see oshimen going on another loan again
Initially, when Osimhen and Napoli had a falling out, Osimhen found an agreement with another club (I don't remember which one) but Napoli broke the deal. Now Osimhen has the best hand and Napoli can't do anything, they will lose 75 million. Osimhen will firstly get his entire salary and secondly, in a year he will leave for better conditions to any club that interests him. The conditions will be better because Osimhen will come as a free agent.