One of the most negative things a seller can do is to not show the shipping and handling charges on their items. There is a great potential for customer loss due the lack of this information. Making a customer have to contact you is another very poor business strategy. In todays fast paceed world people want facts and fast service, they dont want to wait for someone to let them know what somethiong costs. They want the information right there so they can make the descision to buy from you or look for a another like item with a better overall cost.
Not all but a few sellers that use this lack of information in hopes that the buyer will not contact them before the end of the auction. So they can ajust the S & H price of the goods in their favor.
Their are those that list higher than actual shipping costs to boost their profits or cover what they asume their handling costs are.
Any one can access the shipping costs various carriers charge by going to the carriers web site. So if a seller uses a shipping caculator and ajusts the rates to suit themselves, ones customers can figure what you are charging for handling fees. It better to show what your handling fees are in your listing if you charge any. Most buyers on eBay are return buyers, [though new to you] and have a good knowledge of shipping costs from prior purchases.
When Im looking for items to purchase I almost never put an item in my watch that has the shipping costs listed as "not specified" or "contact seller": if Im looking at buying it. Only if Im watching the item to see what it sells for as many sellers do here on eBay.
Another bad practice is to charge for priority mail and then ship it parcel post. Thats a good way to not get a repeat customer.
As a buyer Im here on eBay because of the low cost of many of the items compared to there cost on the open market at retail and internet stores. As a seller Im here because its fun, though I dont sell certain items below there worth such as Texaco Die Cast. I do list good prices on items from my warehouses that I have an over abundence of.