According to that tool I can cash in all my sites with domains and end up with a big lump sum. My domains are old though, been around for a long time already. I have quite a bit of old ones, I don't really maintain the sites that they host though, they are just there and information the same as it was years and years ago, lol.
The idea was to check the stats and the url not an absolute price for any given site. No url checker will ever give a true and accurate price for any site whatsoever but can provide some information towards making a decision when trying to sell a site or url on.
The url itself can be the reason you may make a good sale or thesite content ignoring the url. The type of site and its niche will determine its overall popularity and also its worth when it comes to a sale. I know the guy who created gocompare and he sold for millions but if another person had called a site that and made a forum or blog it may have been worthless so depending on what you offer then it will make a difference to your sale.
Advertising revenue and backlinks ect will fluctuate the price of a site considerably and can create a good stream if you buy up neglected but niche or interesting sites to clean and sell on so even low ranked sites in some situations will be bought still for a quick turnover.
There is no absolute formula for selling a site. You need all the traffic and revenue info plus users ect and also if the site is a type that could be monetised in some way if it isnt already. Most serious buyers are looking to make money not run them for the sake of it like some of us here for gaming or a club ect and dont rely on a revenue stream to make a profit from the users.
I would look for sites sold along the same line as your own and extrapolate a price from that. You could post the url here and some of the users who do buy sites regular may give you a better idea but unless you can provide greater detail its all ifs and buts and no real conclusive estimate.
Sorry my first answer wasnt a lot of detail but obviously dont take url appraisers as gospel just use them for general info as I did say to begin.