"What's your best Price?"

I think it’s a reasonable question and your method to answer is also reasonable, because there is always a possibility the perspective buyer may have something you want and that is why I always ask. And I also am prepared for a simple yes or no it’s the sellers decision if there is room on something that is for sale.
I agree 100%. I'm not going to be a jerk about it. I answered him politely. I honestly don't understand why not just make an offer. You know the price, shoot an offer. Worst I can say is no.