Grey Market Premium: Rs -6 (Seller). This means sellers are ready to sell SVPCL shares at the discount of Rs 6. i.e. 45-6 = Rs 39. 2. Kostak (or price of application) is the premium amount in rupees at which IPO applications are being traded in IPO Grey Market.. Grey market premium (or grey market price) is a premium amount in rupees at which IPO shares are being traded in Grey Market before they get listed in stock exchange.