How much is your shipping?
Zen Cart answer
Be sure to be explicit on the shipping info define page about your shipping policies. Turn on display of the shipping estimator in the cart (1.3.9h new feature). Install the Shipping Estimator Sidebox. If shipping is free, proclaim it over and over and over. Add messages wherever you can in the header, on the product image, in sidebox – just don’t let them forget it.
E-commerce answer
No one really expects to see shipping costs displayed on the product page but since the product weight is a constant, you could put an estimated shipping cost. I would put something like Estimated shipping cost to NY City. That people can see at a glance that they might want to add other items to the order to make the shipping worthwhile – something I’m always doing to justify the purchase of one item online.
The other problem is high shipping costs. If your only shipping option costs $8 to $10 per shipment minimum, why do you think you can sell items that cost less than that when a buyer can find at the local drugstore in the next block with no shipping charge at all?
I offer USPS rates as well as UPS or FedEX so that customers can take advantage of the cheaper express mail rates if necessary. Offering a variety of shipping rates lets the buyer decide how much he or she wants to pay – doesn’t decrease the cost but gives the buyer some control over the outcome.