You are absolutely right to challenge him on the $25 if he never replied to your request for a shipping quote. I bought a pair of Edge anchors one time for something like 8 bucks, and the guy charged me another $10 to ship them, and he didn't even send them Priority Mail, I think the envelope said $.79 postage or something like that. When he first sent me that, I told him that was ridiculous, but he wouldn't budge, so I had no choice thanks to the fact that evilbay only protects sellers and not buyers (a whole other problem...). The funny part is that he then had the cojones to ask me to leave him positive feedback.
Which brings me to another thing. As you mentioned, the seller may only have positives, but that may be because these guys always do what I call feedback ransom. You complete your part of the transaction, you've paid in a timely manner and all, and they won't leave feedback for you until you do it for them. So, you know if you leave them negative, they will leave it negative for you somehow, so you don't bother, that's what I end up doing anyway. A lot of times people will ask me why I haven't left them any feedback, and they are surprised that I'm pissed that the "new" DVD I bought was a copy or something like that.