Honestly, some of the music is pretty crappy. The albums that are worth the most are the ones that I like the least. They're pretty serious hard core punk.
But they're pretty cool.
They've been sitting in my basement for 30 years. They've been stored well, though, so that has helped them keep their value. Many of them are early pressings, or were printed in small editions, or are pre-release promotional albums, or have certain other qualities that make them valuable.
In most cases it's the object that holds my affection, not the content of the object.