All items have their shipping costs listed up front. By clicking to purchase and pay the item, you are agreeing to pay the posted shipping cost: no matter over overcharged.
Ebay has been charging sellers 7% (or around that) on their shipping charges. But, I don't believe ebay is doing any other regulation on shipping costs.
When you're looking at a potential purchase, consider the cost as cost+shipping. So if you have a budget of $50, and you see an item is $49, you probably shouldn't buy it because you need to factor in shipping (unless it's free shipping, of course).