I sometimes have trouble deciding whether "Not a real question" or "Subjective and argumentative" is the best description of why I'm voting to close. That's what happened for me in this case, but regardless of the "official" reason, I thought it should be closed because the value of a domain name is not primarily an issue for sysadmins.
Why domains have different values is an economic issue, and what to do about the value of a domain name is mostly a business issue, i.e. how much do I want to pay for a certain domain name? A sysadmin might (I'd say probably) be involved in researching domain names and costs, but it's not something that only a sysadmin can do, and that research is basically just shopping.
Shopping question are generally closed because they're too localized, and that applies to your example. There is no generally agreed-on definition of "premium domains," and the exact reasons why more is being asked for the ones you asked about domains probably won't apply to other domains.
Hopefully the answers here will give you a better idea of what's considered on- and off-topic and you'll have no problem with future questions. And hopefully in the future I'll do what I almost did here (but didn't bother taking the time) and add a comment as to why I voted, in case it's not clear.