There is one shop in souq asiri selling authentic Levis, along where most of perfume stores stand, they can give you around 30 to 100 riyals less than the royal plaza shop.
I visit this place regularly to look for good buys.
you can found this shop the back of souq asiri near the opossite of the swirling tower building. They are selling over runs / stocks of authentic levis jeans

Feel free to visit, noting to lose.

pykester