Exactly! you said very well ... it's a big bubble! and this bubble will burst sooner or later, this type of business won't hold up for long, the players for the moment are bathing in the big salaries they receive, and having fun! lucky them. I also want to see the Arabs in about ten years if they continue to give stratospheric salaries to top players without having a financial return that can cover their economic expenditure
I think the clubs from the Saudi Professional League wouldn't have to pay these stratospheric salaries forever. They would only need to draw global attention to their league and build a highly attractive national competition with the best players from all around the world. If they could do that within a decade's time, I think they could also normalize their salaries and still be the number one league to go to for players. But this is speculation and I don't know what their goal is with the strategy they are pursuing right now.
But Spanish clubs like Barcelona are proof that financial distress can become a reality. I don't think that the Saudis could run into financial distress like Barcelona did because there are also no financial fair play rules in place, but sustainability is definitely an issue for any league.