So I have been able to pick some expensive cards for very cheap via trades recently and finally decided to ask...
How do you modify the value of a card to account for damage?
What you and the trader are comfortable with. Also depends on how rare and expensive the card is to begin with. No way to just set a specific discount for non ideal cards.
It varies widely by the value of a NM version, and if it is sleeve playable. 50% could be reasonable if it's sleeve playable.
I saw some awful tarms
I just couldn't pay for them unless I needed them for a deck that I knew I tested constantly before purchasing
To me, sleeve playable is the most important thing. I'm a cheap guy so if I can get damaged I will. If I keep the deck for a while I'll upgrade to a better shape card later.