Have the great and good ever thought of making an offer? Maybe you could say "I see you are asking £x for Y but I can get it new for only a tenner more. Would you accept £x-z?"
What hacks me off in the classifieds on many places and eBay are people who get in touch ask a question then don't even bother to show some manners by coming back and letting you know they are no longer interested.
In the last 2 weeks I have had someone on eBay say they wanted to buy something and ask how they pay. My reply to which has never been replied to. Similarly I had someone ask me for a job lot price on something I have on the classifieds on here last week. Sent em a price with a "or let me know how much you think". Again nowt.
But then why do I expect any manners in this day and age? Long gone with Common Sense and Patience.