I personally don't think you can tell shit from any domain appraisal especially automated ones. Same for Alexa ranking, it really means nothing.
I did an appraisal on there of one of my domains that makes me about $2k/month and it said it was worth $200.00.
There are probably some decent appraisal services that do a manual appraisal that might be worth something.
May I suggest:
If the domain has a site on it, ask to see the actual google analytics and webmaster tool numbers. If those are not available ask to see the webserver logs. If someone can't show you any of that then they are probably setting you up for a scam.
If it is just a domain, look at semrush and see what the volumes look like on the key words that you would associate with the domain. You can also look at the google keywords tool and google and bing actual search results and get some good info.
Other than that it basically comes down to "Is the domain worth that much to me?" which should be based on a solid idea that you have that the domain would be good for.
Also I always suggest doing a lot of research into what other domains might be available for the base registration price that might work just as well for you before you commit to buying something at an inflated price.
just my
.