The primary aim of the Saudi government to finance the biggest stars in football is to bring immense viewership. Playing very well is only an additional reward. Fans and the media will be interested if big football stars are brought into the Saudi League. When they show interest, it implies many cable corporations all over the world will pay the Saudi League for the right to broadcast the matches.
At present, the Saudi League keeps on putting resources into bringing numerous football stars. However, there is something to worry about if these stars stay long, they are now rich and they probably would not consider extensions any longer very much like Benzema who is looking for an exit.
I can agree that the main target is to attract people's attention around the world to watch Saudi Pro League. If more people are watching Saudi Pro League, there will be more companies and partnerships joining the league development. When Saudi Pro League has many super stars in football, all the parties in Saudi will get the advantage of its popularity. I think they already reach this target. However, the consistency and quality of the players are also important because it is a part of the entertainment. People will be unsatisfied if the super stars always played underperformance.
Saudi teams have huge money, they will always attract more top players joining Saudi Pro League. The Saudi teams won't be worried about the wealth of the players, why? As long as the players can give the entertainment for Saudi, they won't mind with high salaries.
The only problem is how long saudi can only rely with the money to help the club gets demand by recruiting european players? we have seen that many times that if this is not fully worked. You can see that some players have been trying to exodus back again to the european competition.
This is also destroying the reputation of the league as well as there would be some bad reviews about this, i think that this can become the consequence when you were hiring people caused by money. They were not willing to play in this league but they came due to the money.
So, we can take this as the main evaluation to consider whether it was successful or not.