もう少(すこ)し安(やす)くなりませんか。

This is a polite way to ask for a discount or a lower price, often used when negotiating or trying to get a better deal, especially in markets or small shops where bargaining might be possible to save some money.

値段をもう少し安くしてほしい時に、お店の人に丁寧に尋ねる表現です。