Because the business conducted on Ebay throughout the world is dependant upon Postal Services and postal prices sometimes govern the bids placed upon items being auctioned.
Auctioned items placed upon U.K. auctions by Chinese members often contain low starting bids but show exorbitant Shipping and packing charges, e.g. starting bid of 0.99p but packing and shipping as high as £78.00 GBP.
With the current Royal Mail rises in Postal Rates will mean that the Bidder will now need to know the size and weight of the item when making a bid as the highest bid will sometimes be lower than the packing and shipping charge.
Shop around as may new postal services are lower than Royal Mail.
Also try not to make Insurance compulsary. Most postal services have a compensation system for lost packages.