In my opinion (the way I grade at least), details doesn't necessarily always drastically lower the value of the coin. It certainly can, but there are other factors, and sometimes the scratch just isn't that prevalent. So in my mind it can take a coin from fine to VG. Other times, a scratched, bent, porous coin with Fine Details can net Fair or Poor. Either way, the value is less than the net grade. But Details does not ALWAYS mean a drastic cut in value in my opinion.
For the newcomer who isn't confident in grading, it's important to understand that the difference can be great and you should be VERY careful when making a purchase.
But then, learn to grade (and net grade) for yourself and use these coins as a guide to learning! It's daunting, but rewarding. (And fun.)