While I personally charge cost for postage with an eBay sale, it's certainly not mandatory.

I think if you went ahead and bought the item after being told up front that it was going to cost you $17, I think you should live with it. But, on the other hand, there's nothing wrong with asking.

One time, I bought some goods from Trendclick and asked that he ship them Priority instead of First Class (I wanted tracking). He gave me a tracking number which never registered at USPS. After the item arrived, I saw the charge was quite less than the extra Priority fees I agreed to. I brought this to his attention and he refunded the difference without argument.