After a sandstorm: paying a bit more to avoid paying much more
Shamal winds and summer dust events change the economics for a few days. Demand spikes, so slots vanish and some vendors add AED 10–30 to usual rates or stop discounting. Booking the evening the storm ends, rather than joining the next-morning rush, is the cheapest timing you will get.
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.