This setting is useful when you want to display prices to logged-in users only. After you turn on this setting, non-logged in users, including both guests and registered-but-not-logged-in users, can neither see prices nor add any products to the cart for purchase. 

Letting customers know a product is in stock or out of stock is important to improve user experience. You are allowed to show or hide the OUT OF STOCK label for out-of-stock products in your app. That way, your customers know a particular product is available but is currently sold out.