IMO i think that the domain is worth about as much as the registry cost. With .ws domains been ranked so low within the ending of domains in the eyes of search engines like Google, the work that is to be put into the SEO of the site would take months to rate as well as a .com or .org with an hours SEO done. But like tattooes, a domain is something that a person will either love or hate.
Don't forget future value. I have percussion.info. It used to be impossible to get anything from it but now it's starting to place. .ws might come around as well. There's no guarantees.