I would respond by saying - "Oh about 6 million dollars" - .

We all know that auctions are not predictable....who knows what an item is worth? It is the bidders who determine the value of an item at the time an auction ends.

I have had high quality items ...heaps of watchers & no bids...then i have had what I would could consider as a junky item and the bidders have gone into a frenzy and the item has sold for a silly amount.

To answer your question - I always respond. "Just leave a bid that you are comfortable with"

If it is an item that you have no idea how much it might sell for, then there isn't much you can say to the person asking. Just say as mentioned above, that you prefer to let the auction run.

If it is an item, that you do have a $ amount you hope to sell it for, you could tell the buyer the amount, up to you though, you don't have to respond with an amount.

Whatever the market is prepared to pay...how much are you offering?

Thanks a lot for all your answers - you pretty much covered all my reactions. I'm just a private seller, nothing else. And no, I'm not interested in doing stuff outside eBay.  I think it's the tone of the queries that bothers me  - it's somewhat rude and disparaging (s/he wrote back and said they were asking because 'I can't imagine anyone wanting to buy a second hand X but if your price is reasonable I may buy it now') .  I figure, the point of an auction is to find a price!