Can't really decide who I am going to side with on this one.
In one way - as an Ebay seller myself, if I had advertised something to sell and hadn't actually advertised it as collect.... I would be a bit miffed as to why someone would want to collect it at my house ( especially something electrical ) Who's to say you wouldn't pick it up in person, go home - then swap it with your broken one - then arrive back at my door claiming it was faulty. I just don't want some random knowing my address for a start.
Maybe the seller has some way of getting free postage (i.e. - someone they know works for a delivery firm - so they actually get the postage costs as well as the final selling price ) and is a bit annoyed at someone actually wanting to collect in person ( and is therefor trying to recoup the cost via the addtional charge )