"What's Your Best Price?"

I think that Markphd and Onhiway61 and Tvad are correct; at least that's my reaction. I will not negotiate against myself. I am always courteous and reply as the others said "Make me an offer and I'll let you know". Few people, IME, are willing to come back with that price, even if its reasonable. The few times I have done that, the next step is to offer 66-90% of that #, with shipping and pp fees included. You have to be polite, because there is that one guy in a hundred who will is serious, but virtually all negotiations that started that way, did not result in me making a sale.

it suggests that you think the seller stupid enough to negotiate against himself. The fact that the seller might be willing to take less than the asking price is no defense to this strategy and doesn't relieve the buyer from making a counter-offer to find that out.

That says it all, Jeffrey. Never negotiate against yourself. If your ad says OBO, then its up to the buyer to make an offer.