Obviously domain name pricing is subjective to say the least.
Generally I use an algorithm variously based on the following:
1) Recent comparative sales (if older sales are used then a multiple to take into account the rise in domain prices generally over the period);
2) Overture results;
3) User friendliness (is the domain logical for its proposed use and is it memorable to the public);
4) Developed comparative site names and their value;
5) Developed comparative site names and their popularity (Alexa ranking);
6) The domain suffix;
7) Google and Yahoo page counts
This is just a rough list of how I come to value my domains, there are of course other factors as well and for many domains emphasis of any of the points may be higher or lower than for other domain names.
I do agree the word 'premium' is much over used, however, again the word is itself subjective, especially when marketability of a domain name is concerned. One person may see ASDFGHJKL.com as a 'prime' domain because it uses each of the letters in the middle row of the keyboard in order, and yes it could be argued this is then a very 'marketable name', but to me I would keep the few dollars in my pocket thank you rather than register it. Again I have to stress that putting a value on a domain is very subjective.
Having said all of the above it would seem by the lack of response I get on this forum to the domains I put up here I have got it totally wrong! :?: