I had a big problem with a person who charged me $30 shipping when it cost $5. I was pissed, and called ebay, and they also told me it was not against the rules. That's not true though, you can report an auction for excessive shipping, it's one of the options when reporting. The guy on the phone at ebay was not helpful.
The seller acted like a total ass the whole time, lying, trying to bully me via ebay messages, etc. It was pretty funny because he didn't know how ebay worked very well (I told him this wouldn't help him in the long run). I filed a paypal claim saying that I didn't get what I paid for which is true -- I paid for $30 shipping and got a poorly packed $5 shipping option. I told him I agreed to $30 shipping, because I agreed to pay for a $30 shipping service which he didn't use, and that was what I didn't get. Anyways, it ended with him refunding the difference, me closing the paypal claim, etc.