What makes you feel that no European club will be able to buy Osimhen the amount that Napoli is requesting for apart from the Saudis. If Osimhen performance keeps increasing and he picks form any moment from now on, you will see big clubs in Europe that will go for him, because capable of giving them what they want as a striker. I am happy for this young man because he find it very easy to adapt to Galatasaray football style and is performing wonders for them as a good striker.
Whoever the player is, when the player can show a brilliant performance, there will be many clubs interested in bringing him in, even with high demand from a player. We have seen a lot of that, where a player sets a new record regarding transfers or very high salaries, when they are players who deserve it.
However, it is not uncommon for players to be brought in with high costs and salaries, while they are unable to show their best for the club that bought them, that is a very common thing in football.
The same thing with Victor Osimhen, actually last season there were many clubs who wanted to bring him in, especially when he managed to bring Napoli to win the title.