And to make things interesting, the rules have just changed. A trademark without goodwill is a goner. Of course not, and neither does the value of the trademarks and service marks associated with the business. Trademarks and service marks are heritable in the same way that the goodwill of the business is. Just because a mark has not been registered does not mean that it is neither valid nor valuable.
Registered marks are just easier to find.
Ownership of a mark may have more value in what it can prevent than in what it can provide. Some marks may be desirable, and while a mark may be worth only a few thousand dollars to one business, it may be worth several times that to another business that would like to adopt the mark but is prevented from so doing in an area because of prior rights. 10 Domain names and trademarks and their interplay are confusing, and as of this writing the matter has not been definitively sorted out. If your client has a domain name, it's an asset, and it may be a trademark asset as well. Surely the gentle reader will not be surprised to discover that valuation of intellectual property assets is a complex undertaking, especially given that merely identifying and cataloging such assets is so daunting.