I am forever finding myself calculating postages costs for the sale of items, as well as trying to disect postage rates for items that I purchase, and the general rule, might consider the following four variables. Firstly, the postage rate charged must obviously be enough so as to cover the cost of the stamps. Secondly, it might cover the cost of any envelopes, packing tape or boxes. Thirdly, sellers might also charge a small supplement for the time taken to travel to the post office, which might incur a bus ride, petro for the car or a taxi, but of course more often than not such charges are absorbed through the price paid for 'the' item. When buying, ensure you check exactly what you are paying for, including any required insurance supplements, furthermore if the user is charging an exceptionally high rate of postage, ask if they will send the item by second class post, or send them a message to ensure that they havent made a mistake - which can happen. For selling, ensure that you calculate your post correctly. I have found the post office more than happy to provide quotes for a range of postage circumstances, including both domestic and international postage for standard and special delivery, so that I can be sure that I am providing an accurate rate of postage for successful bidders. Besides, you don't want to leave yourself short! Hope this helps...