As mentioned above, one very common mistake new domain investors make is to try value domains using automated valuators. They all use a one-size-fits-all system, applied equally to all domains being valuated. They apply the same algorithm/s to a brandable with no searches, as they do to a domain with tons of searches. According to those algorithms the brandable may show up with an almost worthless valuation... and the keyword domain with searches may show up with a huge valuation.
Now for the reality: that brandable domain may be very, very valuable, even if it has little or no searches or other metrics going for it; and that keyword domain may be almost worthless, because it may be a term that gets tons of searches and have other good metrics going for it... but is simply not the kind of domain any end user would purchase, use, pay a high $ for.
Forget the automated appraisals, they are wildly inaccurate. Also note: there are many, many systems offering domain appraisals these days (automated), and they all create their own algorithms! So one auto-appraiser may give a $200 value to your domain, another might give $2500, and another might give $15K. And they are changing their systems all the time, so next month each valuator might give you a much different appraisal.
Also, don't pay for any human appraisal. There's simply no point - you'll pay for one person's opinion, or maybe a small 'panel' of two or three people, who say they are experienced. And they might be, but they are also giving you an appraisal based on what works for them.
If you already own a domain, best to simply put it up for appraisal here. You have a wide field of domainers to listen to, from newbies with no sales, to sellers who dabble, to sellers who do well enough to make this their sole income source (that's my own category, btw), to some sellers who are wealthy and sell mainly premium domains. And it's all for free
The most important part: it is way, way too early for you to be investing in expensive domains. If you don't even know a rough value of a domain and have to think about auto-appraisals, or paid human appraisals... you're going to lose a lot of money. I have seen a lot, a LOT, of people start domaining with a big chunk of money - thousands $, even tens of thousands $ or more... and totally blow that money on bad domain decisions. Just because you pay a lot for a domain, and the auto- and human appraisers say it is worth a lot, does not mean you will ever sell that domain for a lot. Or that you will sell it EVER. Or that you will sell it even for what you paid for it.
You need more time. You need to really study domains, before you throw away a lot of cash into them. Here's what I say to newbies who have a lot of money to invest in domains:
It doesn't matter if you're rich and you can afford big money to purchase domains; it is unwise for ANY wealthy person to throw money away on investments you don't yet have a clear understanding of. First, educate yourself, get a very clear understanding of how domains are valued, what kinds of sell-through rate there are depending on the kinds of domains you buy/sell, what kind of ROI you can realistically hope for (not 'get', but 'hope for', because there's no sure thing in domaining, except that you can lose a lot of money if you domain unwisely). To sum it all up:
'Experiment small', rather than experimenting with big bucks. Right now you are dabbling and experimenting; don't make huge mistakes. Take small steps, learn from the many small mistakes you make (and you will make them, even with small domain purchases). When you've got a lot of learning and mistakes under your belt... you'll be glad you saved all your cash, so you can then make much wiser investments with your larger expenditures... LATER.
Hope that helps