There are some truly horrible responses in this thread.
KRL is right on when he says: "A domain is worth whatever you can sell it for. Nothing more, nothing less."
...but there are methodologies and guidelines people use to help them approximate what buyers will pay. For smaller generic names, those that get a handful of typeins a day - PPC players would be happy to pay anywhere from 2-10 years revenue (in most cases 3-5 years) from the typeins. As competition for these names increases, the premium continues to go up and up.
Super premium names like Men.com transcend the limitations of basic valuation models that use Overture scores, google results, etc.
