If I get someone who doesn't think the discount I have offered is generous enough then I ask them to take that amount of discount out of their wallet and just throw it away down the street. The usual reaction is that that would be a less than sensible action - but when I point out that thats exactly what I have just done for them things get back into perspective.
If you could have sold it for the full ask, you never would have offered the discount.
Got a good-hearted lecture from the wrecker in Goulburn once, about how he had to make money and his wife was sick of eating rabbit all the time (and that's why he was sticking to his too-high prices).
Funny thing was that the amount of money I put straight back into my wallet would have fed his whole family in the best restaurant in Goulburn, but he'd prefer to have the dusty old bike parts sitting on his shelf until the day he dies.
Seriously, I understand wreckers are different to normal retailers, as they don't always get the stock they want.
But lots of conventional retailers do stuff completely against what I learned back in the day.