I borrowed it from a girl 5 years ago who had obviously lent it out a lot, so the disks were already scratched pretty bad (but still playable) when I got it. She never wanted it back, though.
I have a used copy of 8 with some scratches that don't affect the game in any way I've seen, and a used copy of 9 in excellent condition. Of course, buying used PS1 games as popular as these is always a gamble, so I just got lucky twice.