€75 million in total is not that much for any of the major clubs. It's probably about the position being free and going through most of those major clubs, I don't know wich one us currently looking for a center forward like Osimhen.
There are not many clubs in Europe who would be willing to pay €75m for a player and for Napoli this would be the 2nd most expensive sale in the club's history!
If Osimhen were to be sold for €75m he would be one of the top 50 most expensive sales ever and that's not something you see every day. In the 24/25 season there were perhaps only a few players who were sold for such high sums, I think there were certainly no more than 3-4 players! So selling Osimhen for that price won't be that easy.
It seems to be expensive, but the times have changed so much and they have many different ways to finance these transfers. Sometimes they pay in tranches over more than one year, sometimes a lot of the transfer fee depends on bonuses, they can make all kinds of arrangements to get these transfers done and you will always have one club at least who is driving the price. If there is one club willing to pay €50 million and then Manchester City cones by and says they would pay €65 million, there isn't much these other clubs can do other than pay the price that Napoli wants to have Osimhen.
10 years ago it would have been different, but these prices have been inflated for a long time now and Napoli knows there will be someone paying the €75 million. It could be out of unforeseen emergency because during the preparation time a striker gets injured for example and a club has to act. All these things happened before and will happen again. I think it is quite safe that Osimhen will be sold for a price around €70 million.