List price was $21,999. I inquired seriously about it and asked about wiggle room, and the salesperson said, “we can let it go for $20,500.”

How should I regard this? Would it be outrageous to counter with something lower than his last offer? If so, how much lower. On edmunds, they have trade-in value at $17,500, private party at $19,000, and retail at $20,500. Would it be ridiculous to counter with $17,500 (probably what they paid) and target $19,000 as a final sale price (which would be perfect for us). Or would they find such an offer insulting.