Use automated tools as "one data point" to aid your price-setting IF you otherwise lack the tools to set values for yourself.
Tools = personal knowledge of the industry related to your domain(s), personal sales data, experience negotiating, years of tracking reported sales in forums/etc, personal connections to query about offers/value, ability to evaluate any inherent value in a domain, etc.
I personally give no weight to the automated valuation systems and do not make use of them except for their entertainment value.
I personally give no weight to the automated valuation systems and do not make use of them for other than entertainment value.
I agree with that.
I just checked to see what a certain tool would have to say about a couple of domains I purchased within the last four months. One domain was estimated at more than eight times what I paid for it, while the other was estimated at less than one-tenth. I must say that the former was much more pleasant entertainment than the latter! ;)
Ultimately, the value of a domain depends on what size of check an actual buyer is willing to write. Anything else is just conjecture.
The buyer's valuation would depend on what they thought they could do with the domain to earn their investment back. That could vary a lot from one person to the next.
More than once I've picked Webwork's brains for his opinion about a domain I was interested in, and I was willing to pay significantly more than he would have been, simply because the domain would be such a perfect fit for a specific project I had in mind.
Even in those cases, though, the price I paid was a lot less than the seller was originally hoping for!