Good appraisals are tough to come by in the domaining business. Because the market is so speculative, unless you have a typo domains that is producing continuous income, it is difficult to put a price on what a domain is worth. In short, domains are worth whatever someone is wililng to pay for it. In some cases, this is a large amount of money. In most other cases, people will not pay much. Generally, a shorter domain is better than a longer one; .com's are better than other extensions; higher traffic the better; and more marketable, brandable, and generic the domain the better.