SEO is usually done for a developed website, not just blank domain name. If your website has good SERPs and receiving good traffic from SEs then the value will increase a lot but it will also depend on many factors like niche, revenue, traffic etc.
the things that show domain value is the name it's self. then how many links does the name have. is it listed in Yahoo or Google does it have a DOMZ listing. a domain with say 15,000 links is really going to help your sale. a domain with a hundred links won't. age will also help. also it the domain has any page rank.