The problem surrounds Amazons choice to let merchants pick their own shipping costs and the poor way in which Amazon makes those charges visible to the customer.
In essence, when you search for a product and Amazon returns the result, you never see the P&P charges that will be applied.
The important point here is that unlike eBay, who show P&P charges right on screen with the search results, it’s impossible to compare suppliers shipping costs on Amazon.
Try this for yourself: Go to Amazon and try to buy a 1 gig Micro SD card. Attempt to predict how much you will pay based on the returned results. You can’t because the merchants are all dropping the product price and pumping the P&P cost to such an extent that on all the first few pages of results, the P&P cost will double the price you pay. Worse is that you can’t even find out what the shipping price will be.
The end effect of this problem is that it’s nit possible to trust any purchase on the Amazon Store. TurboTas advice is to go use eBay so that you can see upfront how much you will pay.