Doesn't RYM have some sort of connection to pricing memorabilia?
Or is it Discogs?
I'm sure I've seen one of the sites offer prices, although how accurate they are I don't know.
For most music stuff the value is really only what someone wants to pay today. Most music stuff especially metal, doesn't go up and down in value like gold or relics from a time long gone.
Edit: You're probably as well off asking on the site linked in the google images as you are here.