A few years ago, I was selling a car, a moderately rusty 1998 Park Ave with 200Kmi. I was asking $1300. I had an experience similar to what the OP has mentioned with a couple that came over to look at the car, one of them couldn't speak English, the other one was interpreting.
They asked, "what's your bottom dollar?"
I said, "make an offer".
They asked again, "what's your bottom dollar?"
I repeated, "make an offer"
This went on and on and on, for some time, they never made an offer.
I only let it continue, because I was entertained by the fact they were interested, but not enough to make an offer...and I wondered how long they would keep asking for my bottom dollar...well, I got my answer...about half an hour...then they left.