The way I look at it is, if the parts are crap, the seller should take them back, minus the shipping charge (buyer eats that for having them sent out). That way nobody gets harmed. You get your $ back, the seller gets the parts back to get rid of them elsewhere.

I've been fortunate to deal with some really great private parties from this board. Your experience is probably the exception, not the rule. But regardless, in my mind, the seller should yank the stuff back and sell it to someone else. There ARE good parts out there.