Yeah I have encountered the same, keep in mind you could very well be dealing with someone who has never been out their state, so explaining the costs of something being posted from the other side of the world might be a difficult concept to comprehend.

One gripe I have is about a very well known G1 collector who keeps asking me to sell a book I have on ebay to him very cheaply. He just doesn't get that he needs to pay the price I want.