Newcastle United don't have a lack of money, they have no reason to sell their best striker to one of direct competitor in Premier League. Newcastle United are ambitious and want to join top four again in next season, to participate in Champions League again next two seasons.
Arteta can feel that Arsenal have weakness at the striker position but he needs to find a player to replace Gabriel Jesus somewhere else, not from Newcastle United. Around the world, recent years there are very limited world class strikers and this makes competition on transfer market to purchase a top-notch striker, is very difficult.
Isak was expected to replace Ibrahimovic in Swedish national team but now he is no longer young and still can not meet this expectation because his level is far to reach Ibrahimovic's level.
In fact, if you think about what the ownership means, we could basically say that Newcastle United has the richest owner of all time. The team is owned by "the public investment fund" and has a trillion dollars in assets, it's the government of Saudi Arabia that owns the fund, and Saudi Arabia is a kingdom with a king, meaning that the ownership of that fund is bin salmans and nobody else's, so we could say that a king of a whole nation owns it, and not like some small African tribe where they still lack water wells, I mean Saudi Arabia, one of the richest nations in the world, and king of that nation owns the team.
So we can safely assume that financial fair play is the max they can have, that's literally their max, because if it wasn't for financial fair play, they could pay a billion dollars per player on transfers and pay 100 million on salaries, just like they are doing at Saudi league as well. So they are only following the limits they have, and have no need to sell anyone at all.