I agree, I don't think that Chelsea would target Osimhen when they already have Nkunku, even Osimhen wouldn't want to be played from game to game and get replaced in the middle of the match all the time, he might want to join a club where he is the main striker and play most 90 minutes.
Victor Osimhen should cost around 100 million pounds in the summer, that is definitely not an amount Chelsea can spend in this forthcoming summer transfer window, not that they can't afford it, but because of the amount of money they've already spent in the last two transfer windows. As a result of that they might have to take things pretty slow in the summer, except they are going to sell some players for good money, thus they can they balance their books. I'm pretty sure they would be looking at the charges leveled against City today, and they'll want to make sure that it doesn't get to them in the future.
Chelsea should also take into consideration that Manchester City is now once more under investigation because of violation of financial fair play rules or whatever those rules are called in the premier league. However, shouldn't there be some limit anyway? If you realize that 300 million didn't take you anyway and you go and put in another 200 million and it doesn't work, which we might find out soon, the problems are probably more of a structural thing. Something just doesn't work out.
Given that Osimhen just turned 24 and imagine he also wins trophies on top of being the Serie A top scorer, I am sure he is going to cost any club more than 100 million pounds. His contract runs until 2025, which gives Napoli a nice edge for upcoming negotiations.