Questions about Yves Saint Laurent Rive Gauche

I was in a department store recently, and saw the same perfume selling for more than double the price as shown here. I know about Concentration (EDT vs. EDP) and Product version or batch etc., but how do Galaxus guarantee the authenticity and fragrance quality of the product?

Is there any way to order "YSL Rive Gauche - pour Homme, Eau de Toilette" on Galaxus? Or where else can you find this fragrance in Switzerland?