Quoted from dirkdiggler:
Is there a pricecharting type site to value albums besides discogs
Discogs is the my go to. I haven't found another site that tracks used vinyl. Discogs pricing is based on real world sales; so it is, at least, a reflection of what others are paying for any given release. Used vinyl prices just seem to get crazier by the day, so I will often use Discogs for price comparison when I am on the fence about something I have found in a physical store.