Although you could probably add this information to the cart via some Javascript and divide the total by the quantity. This is not simple code. Also the other issue is that making a change in the cart would not change how the backend would see this information. In other words this would be a cosmetic change on the cart page only. It would not show on the checkout page, which can not be modified by code. It is a SS security feature. Also order confirmations and such would not know about this cosmetic change to the cart.