1) Price
Old graphic card like GTX7XX/GTX900 are not worth $200 - $300.
I saw one selling GTX780 for $300 is too high.
2) Condition of the card like oxidation, rust, scratches especially on the golden pin.
Will have lower value.
3) Bring home have to dust and test.
If you want reliable graphic card get brand new one like GTX1650 which is failing back to it's original MSRP below $300.
Other models hopefully will drop.
2nd hand graphic card is 50/50, you can buy a graphic card either have issue or don't know when it will die.
Mining cards avoid those not only used prolong but overclock also.
I have brought used graphic card but I won't spend more than $100.