Quillan, your suggestion matches pretty much what I was doing originally... the "can't sell stuff to NPC merchant if it has been offered on the trader" bug has frustrated me in that approach, though. I hadn't thought about mailing items to an alternate to bypass the bug... but that would be kind of a pain as well.
Demon, what you suggest is what I've been doing lately. I just would like to make a bit more than a few tin: getting three gold together for a horse seems an awfully long way off at that rate! But I'm lazy, so the "hassle" that exists currently in terms of trying to figure out what an item might be worth combined with the trader/NPC merchant bug makes the effort aggravating.
Interesting that the first two posts I get on this thread are a) constructive and b) match the two approaches I've tried already

Thanks, folks- keep any thoughts or ideas flowing here...