Webwork - 2:54 am on Dec 4, 2011 (gmt 0)
Without being too specific a bit more info about the site's link profile would likely be helpful since defensible traffic and rank (however ephemeral) - from a rock solid link profile - might be where the value lies. (Not just the income.) Also, in "big deal" transactions the opportunity to examine logs/analytics for 12+/- months would be imperative - though one needs to be certain of the "buyer's bona fide intention". (There are / have been cases of SOBs who gobbled up info only to walk away . . and compete.)
Also, the purchase and sale of existing sites often has a component of "I/We can do a much better job of monetizing this site". How safe/solid is the monetization?
I'm sure others can speak to the value of edu leads, but how many pertinent/valuable kwp's does this site rank for in 1-3-5 position at this time? Obviously, the more the merrier.
When the $#s get big it's often a function of a number of variables, each of which carries great weight: great domain, great # of great links, array of kwp's the site ranks for, sources of defensible traffic, undermonetization "as is", value of the leads in the market at the given time, etc.
I'm not aware of any website appraisal service, at least not any that's as able to value a site any better than a small group of experienced site-owning web professionals, i.e., people who know the market value / labor+time costs of linkdev, the value of a lead stream, etc. (Kinda why big questions like this should be dragged in little black boxes to PubCon for late nite discussions in smokey bars. I've seen some pretty amazing brain power assembled, giving advice freely, over the many years I've attened PucCons.)