First thing is... at least here in the U.S., you would have qouted a shipping charge in the listing. On what did you base that quote? When you are instructed to print "Shipping lable" (after the sale and after receiving payment) a pop-up box listing all available rates is listed. Some of those are "flat rate" meaning, one charge depending only on certain weight and size limits, whereas "economy shiping" takes longer but the rates are less. These types rates depend on weight of the item.
The really expensive rates are FedEx type shipping.
Lastly, I always quote a rate (in the listing) about 5% higher than what the actual rate is to cover packing of the item, but... never show the actual rate on the shipping lable. If you "de-select" the "show shipping rates" on the lable, it will only show what you advertised in the listing... It's kind of a buffer for me not to get stuck with the unexpected...