What people think about a domain name is what makes it valuable or not.
One person may think a domain has value, but if others do not, then it will not sell for a high price - unless another buyer who sees the value can be found.
Some domains are easy to see the value in like Toys.com. Other domains like Buynetics.com may only be desired by a few people. Then those few people will be the ones to set a dollar value on the domain.
Domain owners generally all think their domains have nice value. After all, they like the domains and that is why they registered them. The problem is that other people may NOT like the domains and only if the rare person that likes the domain can be found can the seller expect a nice price.
I think that the "experts" are the ones that learn, perhaps over months or years, what names are likely to be popular and sell for more than they buy them for.
It should be easy to see why the first domain partners.EU sold for such a nice price. If you don't understand this one then you may not understand the word or the TLD.
nellcote.com is now owned by the Nellcote Wine Group. I would not pay $5 for that domain had I seen it was available.
One thing you can do is use a free appraisal system like Estibot. It won't tell you very accurate numbers, and just because it says a domain is worth $1,500 doesn't mean you will EVER find a buyer that will pay that much, but it will give you a general idea of what the value of a domain is so that you can compare what your idea is with it's idea and see how close they are.
Estibot tells me:
partners.eu $20,000
aluria.com $ 4,300
wpbox.com $ 1,500
nellcote.com $ 3,200
Sometimes if you check domains that have been sold you will find they are fairly close to the estimate, but not always. And in my experience domains with values under $1,000 will be lucky to sell for $100.
