If he can show that the site is making $5,000-6,000 per year, then it is worth it. Otherwise, why not just buy a fresh URL and start your own site. Unless the domain has aged enough to be close to exiting the sandbox, I wouldn’t pay much..even then I’m not sure how much it would be worth, kinda depends on your SEO skill. The domain was registered in November 2004, but it depends on when the site was indexed by Google as to when it may get out of the sandbox.
BTW, preview-casinos.com is available for $8.95 from GoDaddy.