Well there is every reason why Napoli are offering such money for lukaku and that's because their main star striker osimien, I believe is already leaving the club for PSG to fill up the space that another striker (mbappe) left. But the context of the matter now is which of the club would he prefer most to play for because I believe there are still some players who don't just go for money alone as they prefer a club side in which they can enjoy quality good football and also playing time.
The fact that the new coach appointed by Napoli wants lukaku aswell and so to give him the enabling environment to be able to work well and deliver the desired results, they will be ready to buy any player recommend by him to the management of the team. Napoli looks very determined to wanting to get their team back in a best shape by next season and they have been doing all they can to making sure that is a reality by getting a new coach and players too.
If Napoli succeeds in buying lukaku, he is not going back to Chelsea again as he should at the end of his loan time, Chelsea may not really need him that much as they have got a good striker who's going to fit in the position well enough as a striker, the likes of palmer have been very useful to the team this season and except he's been sold out, I don't think Chelsea will really need a striker at this point in time, he's still a very young talented player who can stay with then awhile, before leaving. And they my then be having a need for a striker in Chelsea.
At this point osimhen appears like someone who isn't Looking for a club side where he's will be most concerned with the money, rather where he will be able to see opportunities and become a better player than he has been at Napoli,, a chance to be able to compete at a higher level and also win personal awards too appears to be of more concern to him than that of a place where he will just get paid and his career may not advance as it should.