Well if 9/10 domains you can't sell, then why would people want to pay for lists full of rubbish?
You sell 10/10 of your domains immediately? I'm impressed!
The fact is that 90% of domain sales is timing. If I went out and registered 500 backlink domains today, I sure as hell wouldn't sell all 500 tomorrow.
I'm not sure why you're obsessing on domains being rubbish. If their stats are listed in front of you, presumably you wouldn't pay for anything you didn't rate.