After a sandstorm: paying a bit more to avoid paying much more
More important is what a post-storm wash must be. Storm dust arrives mixed with coarser grit, and if the storm ended with light rain it dries into a bonded crust. Dry-wiping that crust is exactly how clear coats get scratched. After a proper sandstorm, the value-correct choice is a steam or rinse-capable wash at AED 70–120, not the AED 30–50 wipe — and a competent washer should rinse or steam panels before a cloth touches them.
Skipping the post-storm wash entirely is the false economy: grit left in door shuts, wiper channels and window seals grinds every time you use them, and one thorough wash after each major storm is cheap insurance against paint correction at AED 150–400 per stage.