If SA want to send a message to GB and USA, with a good impact on its air force strength, I see a first purchase of 48.
Enough to wait the US and GB answer,
Enough to not have all the eggs in the same basket,
Too few for an arm race.
Egypt with at least 54-100, Qatar with 36-72, UAE with 80 and now Saudi with 48-200. That leaves Turkey and Iran to come up with their own solutions.
And because Turkey and Azerbaijan are allying with Pakistan to create problems in Kashmir, we are arming Armenia. Now Russia and India will have to arm Armenia with fighters too. The Russians are also bound to create problems in Georgia. And they are sure to eventually arm Syria. And we already know the problems both Russia and China are creating in Africa.
Basically a Saudi purchase of Rafales will enable them to have a more independent foreign policy free from US/UK influence, which means the region will open up for Chinese interference.
The Chinese are already in Iran. If they entrench themselves in the GCC, then the US will be forced to pick sides, and they may choose Turkey 'cause of Russia. So both India and France will end up in a problematic situation.
With 400+ Rafales in the region, if Iran decides to match that with next gen Russian/Chinese tech, then Israel's in trouble too. If Israel is pressured, then the US will become more diplomatically aggressive. And any instability in the ME reflects on our prices back home. All 'cause the Saudis are attempting to chart their own course independent of the US.