I think the most valuable disc I have is
ROXCALIBUR
A various artist disc of the local (North East of England) Rising Heavy Metal Bands.
Cover is a little battle weary but the vinyl is NM
NM copies fetch £50+ ($80) when they (very rarely) pop up for sale
Got to admit when I bought it I had no expectations of this.
It's interesting what ends up being valuable?
I think in this case it's due to the fact that this has the first vinyl releases of a few of the bands that went on to make a bit a name for themselves within the NWOBHM scene