I do understand this. You felt insulted.Not me. Tole I'm to fook oft back where he came from an I weren't sellin to him at any price. Dick.
But at the end of the day it is just like the bloke on wheeler dealers or tother prog with the git who never takes his cap off.
You offer a grand under the asking price and see what happens.
Sayin "that's all I've got" is just a bit harder version of the same bid. You can either see it for what it is, and call their bluff, or get the hump and possibly lose a sale.
At the end of the day, "Are you a serious buyer or just a time waster?" is the question to ask. Then say nothing, just wait.
They'll either offer more money or insult the vehicle at which time you walk away.
(I spent too long on "The psychology of selling" type courses when I was younger, before I knocked it on the head and became a teacher!)