Any bike, vintage or not, is only worth what someone will pay for it.
Your valuable may be someone else's trash.
Was he looking to trade it in?
With apologies to the owners of the many fine Speciaized bikes out there, I can't imagine that an old Specialized really holds the value of a more "boutique" brand...a true vintage Schwinn, a Waterford, a Guerciotti (sorry if I butchered the spelling on that one), etc.
That said...my first place to search is Craigslist and E-bay...what are folks asking and getting for these things?
2007 Seven ID8 - Bontrager InForm
2003 Klein Palomino - Terry Firefly (?)
2010 Seven Cafe Racer - Bontrager InForm
2008 Cervelo P2C - Adamo Prologue Saddle