i got a 3 character domain and ive just installed the subdomain redirection script. Basically users can create an account <anything>.3ch.com to redirect to elsewher.
I also own a site that offers 4 subdomains and 1 subdirectory redirects. Anyway if you own the site and want an appraisal this should go in the appraisal section. The value depends on traffic. 3ch.com redirects to a Chinese website with no options for creating a subdomain.