What's your lowest price?Answer is, the price that I accept. I usually just tell those folks to, "make an offer."
I would much rather answer the question,
If I offer you $X, will you accept?I usually answer that question right away because I respect that a serious buyer doesn't want their offer tied up for 48 hours. It is not unusual that I have the offer/acceptance agreed upon before the formal offer is made by the buyer.