Don't buy US silver dollars from China...

Seriously I buy & sell quite a bit of stuff on Ebay and the feedback system really works. My own is over 600, all positives. Actually read the feedback before bidding on expensive stuff too. You'll find some guys with high percentages of good feedback but when you start reading the comments from their buyers you learn that there have been issues in the past. High shipping charges, too many returns, etc.
If I see a seller that tries to make a few extra bucks on every transaction with bogus "handling" charges I tend to stay away. $10 shipping for example for a small item that will easily fit in a USPS Priority Mail Flat Rate box usually raises a red flag in my mind that the seller is less than honest. The boxes are free and the shipping charge is less than 5 bucks. Just my opinion and worth what you paid for it.