Those kind of domains don't really have any value because of their extension and also they are not CEO friendly like .com , .co , .NET , .ORG etc. ..
Lately there are some more rare domains that are expensive as hell, for example the .io domains are really expensive for some reason, and they are trending. The bitco.in was a good idea too, other than that, all the good ones are all already taken. Roger Ver paid tons to spread his propaganda on Bitcoin.com lol.