How could I estimate shipping cost for a product before adding it to cart?
Why should I login/register to know shipping charges for the product in the cart?
Are you concerned with these questions because your customers ask them all the time?
Basically the Quick Rates module for X-Cart enables shipping cost estimation prior to adding products to the shopping basket. Customers can fill in a zipcode to get shipping quotes for a product in Estimation popup.
Customer front-end: Estimation popup
Admin back-end: "General settings -> QuickRates options" settings page

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