I've paid $5,000 for a domain valued at $500 by those services and I've paid $2,000 for domains valued at $10,000+ by those services because that's what those domain names were worth to what we were doing.
The domain appraisal services really have very little knowledge of various niches that really determine value of domains. Most of the valuations I've seen in the appraisal forums value domains based on type in traffic and whether they are in the gambling/porn industry. Other than that, they typically spin their wheels.