I recently reviewed the current site for a potential client who was setting up for online commerce. The prices of the products were more than reasonable compared to similar products available. The shipping listed was astronomically low; low enough to generate substantial loses. The client was a local business heading for a successful online business...with a few tweaks.
All the major shippers; Fed-X, UPS, even the USPS, have handy aps that can be added to a website to calculate shipping costs. Ask your Web Consultant to add them to your e-commerce site.