Me, personally... I'd rather you made an offer, even a low one, as opposed to having you ask me what my best price is. The actual best price is a moving target that depends on the present circumstances and also the credibility of the buyer.
Again, it's just a bit annoying that you wanna know my best price... without revealing how much you are willing to pay. You're obviously afraid that my best price might be less than your best price and you're hoping to eek every penny out of the deal. In my for sale ads, I've made my assessment and listed the starting price for the haggling to begin... I almost always invite offers. If you are interested in buying... have the nerve to actually make the next move it ought to include your own offer.
That said, I would never freak out or get bent out of shape at all... I would just throw it back on you.
I know... I know... if you make your own personal low end offer you may run the risk fo getting run off by a seller who thinks you're lowballing... this wouldn't really matter to me though. If I've made an honest offer and it was rejected or taken as some kind of insult, no big deal. Everyone will get over it and life will go on.